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	$227.73	13.172%	$257.7266	$257.73	$257.75	$257.70
Purchase #2	$75.43	9.507%	$82.6011	$82.60	$82.60	$82.60
Purchase #3	$146.28	13.688%	$166.3028	$166.30	$166.30	$166.30
Purchase #4	$58.56	11.844%	$65.4958	$65.50	$65.50	$65.50
Purchase #5	$169.85	11.832%	$189.9467	$189.95	$189.95	$189.90
Purchase #6	$35.25	4.303%	$36.7668	$36.77	$36.75	$36.80
Purchase #7	$220.25	8.198%	$238.3061	$238.31	$238.30	$238.30
7 purchase totals =	$933.35		$1,037.1459	$1,037.16	$1,037.15	$1,037.10