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	$94.87	5.555%	$100.14	$100.14	$100.15	$100.10
Purchase #2	$249.81	5.133%	$262.6327	$262.63	$262.65	$262.60
Purchase #3	$191.74	11.521%	$213.8304	$213.83	$213.85	$213.80
Purchase #4	$191.65	12.153%	$214.9412	$214.94	$214.95	$214.90
Purchase #5	$56.86	6.390%	$60.4934	$60.49	$60.50	$60.50
Purchase #6	$141.94	7.359%	$152.3854	$152.39	$152.40	$152.40
Purchase #7	$219.82	4.383%	$229.4547	$229.45	$229.45	$229.50
7 purchase totals =	$1,146.69		$1,233.8778	$1,233.87	$1,233.95	$1,233.80