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	$106.61	9.850%	$117.1111	$117.11	$117.10	$117.10
Purchase #2	$176.71	12.603%	$198.9808	$198.98	$199.00	$199.00
Purchase #3	$117.54	4.235%	$122.5178	$122.52	$122.50	$122.50
Purchase #4	$229.89	11.559%	$256.463	$256.46	$256.45	$256.50
Purchase #5	$59.40	4.200%	$61.8948	$61.89	$61.90	$61.90
Purchase #6	$173.37	5.254%	$182.4789	$182.48	$182.50	$182.50
Purchase #7	$49.29	12.427%	$55.4153	$55.42	$55.40	$55.40
7 purchase totals =	$912.81		$994.8617	$994.86	$994.85	$994.90