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	$40.67	4.598%	$42.54	$42.54	$42.55	$42.50
Purchase #2	$124.37	10.556%	$137.4985	$137.50	$137.50	$137.50
Purchase #3	$190.96	7.141%	$204.5965	$204.60	$204.60	$204.60
Purchase #4	$199.69	11.688%	$223.0298	$223.03	$223.05	$223.00
Purchase #5	$221.67	6.556%	$236.2027	$236.20	$236.20	$236.20
Purchase #6	$211.74	10.286%	$233.5196	$233.52	$233.50	$233.50
Purchase #7	$75.63	8.770%	$82.2628	$82.26	$82.25	$82.30
7 purchase totals =	$1,064.73		$1,159.6499	$1,159.65	$1,159.65	$1,159.60