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	$202.96	9.446%	$222.1316	$222.13	$222.15	$222.10
Purchase #2	$169.31	11.248%	$188.354	$188.35	$188.35	$188.40
Purchase #3	$11.83	10.846%	$13.1131	$13.11	$13.10	$13.10
Purchase #4	$182.49	7.573%	$196.31	$196.31	$196.30	$196.30
Purchase #5	$214.88	11.833%	$240.3068	$240.31	$240.30	$240.30
Purchase #6	$239.47	10.856%	$265.4669	$265.47	$265.45	$265.50
Purchase #7	$232.57	9.484%	$254.6269	$254.63	$254.65	$254.60
7 purchase totals =	$1,253.51		$1,380.3093	$1,380.31	$1,380.30	$1,380.30