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	$205.41	6.723%	$219.2197	$219.22	$219.20	$219.20
Purchase #2	$80.38	3.788%	$83.4248	$83.42	$83.40	$83.40
Purchase #3	$164.67	10.700%	$182.2897	$182.29	$182.30	$182.30
Purchase #4	$89.98	6.376%	$95.7171	$95.72	$95.70	$95.70
Purchase #5	$37.87	12.750%	$42.6984	$42.70	$42.70	$42.70
Purchase #6	$127.29	5.624%	$134.4488	$134.45	$134.45	$134.40
Purchase #7	$111.47	4.369%	$116.3401	$116.34	$116.35	$116.30
7 purchase totals =	$817.07		$874.1386	$874.14	$874.10	$874.00