Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$106.39	10.779%	$117.8578	$117.86	$117.85	$117.90
Purchase #2	$169.66	9.147%	$185.1788	$185.18	$185.20	$185.20
Purchase #3	$172.42	9.153%	$188.2016	$188.20	$188.20	$188.20
Purchase #4	$102.79	7.268%	$110.2608	$110.26	$110.25	$110.30
Purchase #5	$209.59	6.562%	$223.3433	$223.34	$223.35	$223.30
Purchase #6	$122.78	3.486%	$127.0601	$127.06	$127.05	$127.10
Purchase #7	$211.54	12.695%	$238.395	$238.40	$238.40	$238.40
7 purchase totals =	$1,095.17		$1,190.2974	$1,190.30	$1,190.30	$1,190.40