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	$151.72	11.513%	$169.1875	$169.19	$169.20	$169.20
Purchase #2	$199.45	4.553%	$208.531	$208.53	$208.55	$208.50
Purchase #3	$86.71	11.763%	$96.9097	$96.91	$96.90	$96.90
Purchase #4	$156.92	11.756%	$175.3675	$175.37	$175.35	$175.40
Purchase #5	$108.30	13.686%	$123.1219	$123.12	$123.10	$123.10
Purchase #6	$216.48	13.131%	$244.906	$244.91	$244.90	$244.90
Purchase #7	$106.48	11.223%	$118.4303	$118.43	$118.45	$118.40
7 purchase totals =	$1,026.06		$1,136.4539	$1,136.46	$1,136.45	$1,136.40