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	$90.91	4.204%	$94.7319	$94.73	$94.75	$94.70
Purchase #2	$233.56	6.778%	$249.3907	$249.39	$249.40	$249.40
Purchase #3	$149.31	6.299%	$158.715	$158.72	$158.70	$158.70
Purchase #4	$58.25	5.318%	$61.3477	$61.35	$61.35	$61.30
Purchase #5	$52.90	11.804%	$59.1443	$59.14	$59.15	$59.10
Purchase #6	$6.38	3.300%	$6.5905	$6.59	$6.60	$6.60
Purchase #7	$40.40	7.314%	$43.3549	$43.35	$43.35	$43.40
7 purchase totals =	$631.71		$673.2750	$673.27	$673.30	$673.20