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	$223.39	13.830%	$254.2848	$254.28	$254.30	$254.30
Purchase #2	$71.71	8.204%	$77.5931	$77.59	$77.60	$77.60
Purchase #3	$88.95	10.479%	$98.2711	$98.27	$98.25	$98.30
Purchase #4	$120.39	5.789%	$127.3594	$127.36	$127.35	$127.40
Purchase #5	$150.71	3.110%	$155.3971	$155.40	$155.40	$155.40
Purchase #6	$196.51	11.752%	$219.6039	$219.60	$219.60	$219.60
Purchase #7	$234.72	12.806%	$264.7782	$264.78	$264.80	$264.80
7 purchase totals =	$1,086.38		$1,197.2876	$1,197.28	$1,197.30	$1,197.40