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	$160.59	7.649%	$172.8735	$172.87	$172.85	$172.90
Purchase #2	$80.89	11.145%	$89.9052	$89.91	$89.90	$89.90
Purchase #3	$140.96	13.326%	$159.7443	$159.74	$159.75	$159.70
Purchase #4	$20.92	7.774%	$22.5463	$22.55	$22.55	$22.50
Purchase #5	$176.77	12.826%	$199.4425	$199.44	$199.45	$199.40
Purchase #6	$61.46	10.444%	$67.8789	$67.88	$67.90	$67.90
Purchase #7	$211.29	11.231%	$235.02	$235.02	$235.00	$235.00
7 purchase totals =	$852.88		$947.4107	$947.41	$947.40	$947.30