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	$193.79	11.495%	$216.0662	$216.07	$216.05	$216.10
Purchase #2	$84.86	7.699%	$91.3934	$91.39	$91.40	$91.40
Purchase #3	$159.35	6.769%	$170.1364	$170.14	$170.15	$170.10
Purchase #4	$238.30	13.183%	$269.7151	$269.72	$269.70	$269.70
Purchase #5	$165.74	11.819%	$185.3288	$185.33	$185.35	$185.30
Purchase #6	$52.89	11.732%	$59.0951	$59.10	$59.10	$59.10
Purchase #7	$144.93	9.400%	$158.5534	$158.55	$158.55	$158.60
7 purchase totals =	$1,039.86		$1,150.2884	$1,150.30	$1,150.30	$1,150.30