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	$128.60	8.510%	$139.5439	$139.54	$139.55	$139.50
Purchase #2	$120.88	10.530%	$133.6087	$133.61	$133.60	$133.60
Purchase #3	$138.79	11.454%	$154.687	$154.69	$154.70	$154.70
Purchase #4	$141.56	4.133%	$147.4107	$147.41	$147.40	$147.40
Purchase #5	$237.87	10.823%	$263.6147	$263.61	$263.60	$263.60
Purchase #6	$123.32	5.854%	$130.5392	$130.54	$130.55	$130.50
Purchase #7	$158.74	7.836%	$171.1789	$171.18	$171.20	$171.20
7 purchase totals =	$1,049.76		$1,140.5831	$1,140.58	$1,140.60	$1,140.50