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	$180.65	8.688%	$196.3449	$196.34	$196.35	$196.30
Purchase #2	$170.89	6.845%	$182.5874	$182.59	$182.60	$182.60
Purchase #3	$40.51	11.221%	$45.0556	$45.06	$45.05	$45.10
Purchase #4	$29.31	12.612%	$33.0066	$33.01	$33.00	$33.00
Purchase #5	$248.99	13.850%	$283.4751	$283.48	$283.50	$283.50
Purchase #6	$147.37	5.409%	$155.3412	$155.34	$155.35	$155.30
Purchase #7	$202.81	9.258%	$221.5861	$221.59	$221.60	$221.60
7 purchase totals =	$1,020.53		$1,117.3969	$1,117.41	$1,117.45	$1,117.40