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	$114.32	11.175%	$127.0953	$127.10	$127.10	$127.10
Purchase #2	$225.56	5.679%	$238.3696	$238.37	$238.35	$238.40
Purchase #3	$203.66	5.299%	$214.4519	$214.45	$214.45	$214.50
Purchase #4	$232.26	4.579%	$242.8952	$242.90	$242.90	$242.90
Purchase #5	$50.83	13.839%	$57.8644	$57.86	$57.85	$57.90
Purchase #6	$243.33	3.526%	$251.9098	$251.91	$251.90	$251.90
Purchase #7	$238.33	9.573%	$261.1453	$261.15	$261.15	$261.10
7 purchase totals =	$1,308.29		$1,393.7315	$1,393.74	$1,393.70	$1,393.80