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	$173.58	10.391%	$191.6167	$191.62	$191.60	$191.60
Purchase #2	$72.64	5.846%	$76.8865	$76.89	$76.90	$76.90
Purchase #3	$67.66	10.132%	$74.5153	$74.52	$74.50	$74.50
Purchase #4	$89.31	12.372%	$100.3594	$100.36	$100.35	$100.40
Purchase #5	$21.75	13.847%	$24.7617	$24.76	$24.75	$24.80
Purchase #6	$224.98	9.847%	$247.1338	$247.13	$247.15	$247.10
Purchase #7	$19.96	8.290%	$21.6147	$21.61	$21.60	$21.60
7 purchase totals =	$669.88		$736.8881	$736.89	$736.85	$736.90