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	$75.29	9.591%	$82.5111	$82.51	$82.50	$82.50
Purchase #2	$196.28	8.567%	$213.0953	$213.10	$213.10	$213.10
Purchase #3	$185.30	11.139%	$205.9406	$205.94	$205.95	$205.90
Purchase #4	$190.40	12.268%	$213.7583	$213.76	$213.75	$213.80
Purchase #5	$58.92	3.624%	$61.0553	$61.06	$61.05	$61.10
Purchase #6	$204.40	6.451%	$217.5858	$217.59	$217.60	$217.60
Purchase #7	$91.75	8.126%	$99.2056	$99.21	$99.20	$99.20
7 purchase totals =	$1,002.34		$1,093.1520	$1,093.17	$1,093.15	$1,093.20