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	$140.33	7.220%	$150.4618	$150.46	$150.45	$150.50
Purchase #2	$194.44	5.812%	$205.7409	$205.74	$205.75	$205.70
Purchase #3	$62.55	6.263%	$66.4675	$66.47	$66.45	$66.50
Purchase #4	$177.37	10.842%	$196.6005	$196.60	$196.60	$196.60
Purchase #5	$127.95	9.342%	$139.9031	$139.90	$139.90	$139.90
Purchase #6	$175.34	9.362%	$191.7553	$191.76	$191.75	$191.80
Purchase #7	$154.96	7.496%	$166.5758	$166.58	$166.60	$166.60
7 purchase totals =	$1,032.94		$1,117.5049	$1,117.51	$1,117.50	$1,117.60