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	$32.36	11.454%	$36.0665	$36.07	$36.05	$36.10
Purchase #2	$41.46	10.718%	$45.9037	$45.90	$45.90	$45.90
Purchase #3	$176.53	11.108%	$196.139	$196.14	$196.15	$196.10
Purchase #4	$247.44	11.256%	$275.2918	$275.29	$275.30	$275.30
Purchase #5	$192.62	12.208%	$216.135	$216.14	$216.15	$216.10
Purchase #6	$193.91	11.447%	$216.1069	$216.11	$216.10	$216.10
Purchase #7	$150.50	3.432%	$155.6652	$155.67	$155.65	$155.70
7 purchase totals =	$1,034.82		$1,141.3081	$1,141.32	$1,141.30	$1,141.30