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	$54.85	9.521%	$60.0723	$60.07	$60.05	$60.10
Purchase #2	$187.39	11.648%	$209.2172	$209.22	$209.20	$209.20
Purchase #3	$124.37	4.405%	$129.8485	$129.85	$129.85	$129.80
Purchase #4	$165.74	11.560%	$184.8995	$184.90	$184.90	$184.90
Purchase #5	$45.38	12.676%	$51.1324	$51.13	$51.15	$51.10
Purchase #6	$210.89	10.601%	$233.2464	$233.25	$233.25	$233.20
Purchase #7	$215.90	9.838%	$237.1402	$237.14	$237.15	$237.10
7 purchase totals =	$1,004.52		$1,105.5565	$1,105.56	$1,105.55	$1,105.40