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	$53.28	11.366%	$59.3358	$59.34	$59.35	$59.30
Purchase #2	$83.26	7.542%	$89.5395	$89.54	$89.55	$89.50
Purchase #3	$204.44	3.716%	$212.037	$212.04	$212.05	$212.00
Purchase #4	$7.41	3.490%	$7.6686	$7.67	$7.65	$7.70
Purchase #5	$64.37	9.645%	$70.5785	$70.58	$70.60	$70.60
Purchase #6	$33.70	9.736%	$36.981	$36.98	$37.00	$37.00
Purchase #7	$191.35	9.346%	$209.2336	$209.23	$209.25	$209.20
7 purchase totals =	$637.81		$685.3740	$685.38	$685.45	$685.30