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	$192.84	10.149%	$212.4113	$212.41	$212.40	$212.40
Purchase #2	$165.85	13.517%	$188.2679	$188.27	$188.25	$188.30
Purchase #3	$227.78	12.692%	$256.6898	$256.69	$256.70	$256.70
Purchase #4	$172.74	13.621%	$196.2689	$196.27	$196.25	$196.30
Purchase #5	$151.39	7.115%	$162.1614	$162.16	$162.15	$162.20
Purchase #6	$148.80	8.151%	$160.9287	$160.93	$160.95	$160.90
Purchase #7	$31.48	9.817%	$34.5704	$34.57	$34.55	$34.60
7 purchase totals =	$1,090.88		$1,211.2984	$1,211.30	$1,211.25	$1,211.40