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	$233.96	13.143%	$264.7094	$264.71	$264.70	$264.70
Purchase #2	$162.66	11.638%	$181.5904	$181.59	$181.60	$181.60
Purchase #3	$207.69	3.327%	$214.5998	$214.60	$214.60	$214.60
Purchase #4	$229.47	11.364%	$255.547	$255.55	$255.55	$255.50
Purchase #5	$104.69	9.751%	$114.8983	$114.90	$114.90	$114.90
Purchase #6	$59.54	3.801%	$61.8031	$61.80	$61.80	$61.80
Purchase #7	$249.94	6.231%	$265.5138	$265.51	$265.50	$265.50
7 purchase totals =	$1,247.95		$1,358.6618	$1,358.66	$1,358.65	$1,358.60