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	$42.43	11.589%	$47.3472	$47.35	$47.35	$47.30
Purchase #2	$57.38	3.595%	$59.4428	$59.44	$59.45	$59.40
Purchase #3	$28.96	10.873%	$32.1088	$32.11	$32.10	$32.10
Purchase #4	$150.96	4.449%	$157.6762	$157.68	$157.70	$157.70
Purchase #5	$83.66	10.344%	$92.3138	$92.31	$92.30	$92.30
Purchase #6	$196.41	6.659%	$209.4889	$209.49	$209.50	$209.50
Purchase #7	$224.95	10.357%	$248.2481	$248.25	$248.25	$248.20
7 purchase totals =	$784.75		$846.6258	$846.63	$846.65	$846.50