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	$110.81	11.780%	$123.8634	$123.86	$123.85	$123.90
Purchase #2	$223.70	12.258%	$251.1211	$251.12	$251.10	$251.10
Purchase #3	$100.34	4.153%	$104.5071	$104.51	$104.50	$104.50
Purchase #4	$149.31	8.435%	$161.9043	$161.90	$161.90	$161.90
Purchase #5	$32.88	13.345%	$37.2678	$37.27	$37.25	$37.30
Purchase #6	$219.62	4.670%	$229.8763	$229.88	$229.90	$229.90
Purchase #7	$207.64	13.164%	$234.9737	$234.97	$234.95	$235.00
7 purchase totals =	$1,044.30		$1,143.5137	$1,143.51	$1,143.45	$1,143.60