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	$189.52	5.449%	$199.8469	$199.85	$199.85	$199.80
Purchase #2	$85.30	7.513%	$91.7086	$91.71	$91.70	$91.70
Purchase #3	$190.35	4.633%	$199.1689	$199.17	$199.15	$199.20
Purchase #4	$40.93	5.739%	$43.279	$43.28	$43.30	$43.30
Purchase #5	$97.34	3.642%	$100.8851	$100.89	$100.90	$100.90
Purchase #6	$182.37	5.461%	$192.3292	$192.33	$192.35	$192.30
Purchase #7	$6.95	7.167%	$7.4481	$7.45	$7.45	$7.40
7 purchase totals =	$792.76		$834.6658	$834.68	$834.70	$834.60