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	$50.61	3.141%	$52.1997	$52.20	$52.20	$52.20
Purchase #2	$162.89	7.755%	$175.5221	$175.52	$175.50	$175.50
Purchase #3	$35.71	3.365%	$36.9116	$36.91	$36.90	$36.90
Purchase #4	$17.29	7.201%	$18.5351	$18.54	$18.55	$18.50
Purchase #5	$46.31	5.467%	$48.8418	$48.84	$48.85	$48.80
Purchase #6	$238.33	7.217%	$255.5303	$255.53	$255.55	$255.50
Purchase #7	$79.40	7.868%	$85.6472	$85.65	$85.65	$85.60
7 purchase totals =	$630.54		$673.1878	$673.19	$673.20	$673.00