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	$93.76	7.283%	$100.5885	$100.59	$100.60	$100.60
Purchase #2	$91.82	3.718%	$95.2339	$95.23	$95.25	$95.20
Purchase #3	$22.63	3.188%	$23.3514	$23.35	$23.35	$23.40
Purchase #4	$120.42	3.449%	$124.5733	$124.57	$124.55	$124.60
Purchase #5	$151.92	10.114%	$167.2852	$167.29	$167.30	$167.30
Purchase #6	$179.41	6.790%	$191.5919	$191.59	$191.60	$191.60
Purchase #7	$80.27	13.786%	$91.336	$91.34	$91.35	$91.30
7 purchase totals =	$740.23		$793.9602	$793.96	$794.00	$794.00