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	$165.55	6.133%	$175.7032	$175.70	$175.70	$175.70
Purchase #2	$177.96	7.518%	$191.339	$191.34	$191.35	$191.30
Purchase #3	$207.48	6.359%	$220.6737	$220.67	$220.65	$220.70
Purchase #4	$101.46	11.654%	$113.2841	$113.28	$113.30	$113.30
Purchase #5	$168.51	11.501%	$187.8903	$187.89	$187.90	$187.90
Purchase #6	$86.29	4.760%	$90.3974	$90.40	$90.40	$90.40
Purchase #7	$159.34	8.244%	$172.476	$172.48	$172.50	$172.50
7 purchase totals =	$1,066.59		$1,151.7637	$1,151.76	$1,151.80	$1,151.80