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	$158.61	9.871%	$174.2664	$174.27	$174.25	$174.30
Purchase #2	$56.47	5.232%	$59.4245	$59.42	$59.40	$59.40
Purchase #3	$84.68	6.114%	$89.8573	$89.86	$89.85	$89.90
Purchase #4	$12.94	5.738%	$13.6825	$13.68	$13.70	$13.70
Purchase #5	$89.96	5.833%	$95.2074	$95.21	$95.20	$95.20
Purchase #6	$128.55	7.181%	$137.7812	$137.78	$137.80	$137.80
Purchase #7	$117.55	5.829%	$124.402	$124.40	$124.40	$124.40
7 purchase totals =	$648.76		$694.6213	$694.62	$694.60	$694.70