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	$135.43	9.358%	$148.1035	$148.10	$148.10	$148.10
Purchase #2	$224.78	10.751%	$248.9461	$248.95	$248.95	$248.90
Purchase #3	$144.96	9.751%	$159.095	$159.10	$159.10	$159.10
Purchase #4	$42.72	13.557%	$48.5116	$48.51	$48.50	$48.50
Purchase #5	$155.34	10.633%	$171.8573	$171.86	$171.85	$171.90
Purchase #6	$76.68	11.730%	$85.6746	$85.67	$85.65	$85.70
Purchase #7	$183.36	3.362%	$189.5246	$189.52	$189.50	$189.50
7 purchase totals =	$963.27		$1,051.7127	$1,051.71	$1,051.65	$1,051.70