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	$171.70	9.626%	$188.2278	$188.23	$188.25	$188.20
Purchase #2	$198.61	11.471%	$221.3926	$221.39	$221.40	$221.40
Purchase #3	$208.61	5.684%	$220.4674	$220.47	$220.45	$220.50
Purchase #4	$59.73	11.366%	$66.5189	$66.52	$66.50	$66.50
Purchase #5	$207.28	11.317%	$230.7379	$230.74	$230.75	$230.70
Purchase #6	$85.81	3.276%	$88.6211	$88.62	$88.60	$88.60
Purchase #7	$72.59	5.396%	$76.507	$76.51	$76.50	$76.50
7 purchase totals =	$1,004.33		$1,092.4727	$1,092.48	$1,092.45	$1,092.40