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	$185.65	5.741%	$196.3082	$196.31	$196.30	$196.30
Purchase #2	$89.43	7.217%	$95.8842	$95.88	$95.90	$95.90
Purchase #3	$226.27	6.129%	$240.1381	$240.14	$240.15	$240.10
Purchase #4	$225.89	7.638%	$243.1435	$243.14	$243.15	$243.10
Purchase #5	$21.43	11.338%	$23.8597	$23.86	$23.85	$23.90
Purchase #6	$14.72	4.500%	$15.3824	$15.38	$15.40	$15.40
Purchase #7	$204.79	9.701%	$224.6567	$224.66	$224.65	$224.70
7 purchase totals =	$968.18		$1,039.3728	$1,039.37	$1,039.40	$1,039.40