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	$239.63	13.222%	$271.3139	$271.31	$271.30	$271.30
Purchase #2	$175.55	11.726%	$196.135	$196.14	$196.15	$196.10
Purchase #3	$146.44	3.359%	$151.3589	$151.36	$151.35	$151.40
Purchase #4	$204.91	5.368%	$215.9096	$215.91	$215.90	$215.90
Purchase #5	$89.44	6.278%	$95.055	$95.06	$95.05	$95.10
Purchase #6	$128.36	12.549%	$144.4679	$144.47	$144.45	$144.50
Purchase #7	$26.29	3.388%	$27.1807	$27.18	$27.20	$27.20
7 purchase totals =	$1,010.62		$1,101.4210	$1,101.43	$1,101.40	$1,101.50