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	$116.67	6.665%	$124.4461	$124.45	$124.45	$124.40
Purchase #2	$176.62	13.834%	$201.0536	$201.05	$201.05	$201.10
Purchase #3	$29.68	6.300%	$31.5498	$31.55	$31.55	$31.50
Purchase #4	$29.55	10.328%	$32.6019	$32.60	$32.60	$32.60
Purchase #5	$67.45	5.191%	$70.9513	$70.95	$70.95	$71.00
Purchase #6	$64.47	11.496%	$71.8815	$71.88	$71.90	$71.90
Purchase #7	$199.86	11.715%	$223.2736	$223.27	$223.25	$223.30
7 purchase totals =	$684.30		$755.7578	$755.75	$755.75	$755.80