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	$67.35	8.261%	$72.9138	$72.91	$72.90	$72.90
Purchase #2	$16.71	8.404%	$18.1143	$18.11	$18.10	$18.10
Purchase #3	$82.65	12.450%	$92.9399	$92.94	$92.95	$92.90
Purchase #4	$98.31	6.814%	$105.0088	$105.01	$105.00	$105.00
Purchase #5	$169.77	13.269%	$192.2968	$192.30	$192.30	$192.30
Purchase #6	$247.55	3.539%	$256.3108	$256.31	$256.30	$256.30
Purchase #7	$236.43	8.672%	$256.9332	$256.93	$256.95	$256.90
7 purchase totals =	$918.77		$994.5176	$994.51	$994.50	$994.40