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	$103.76	7.183%	$111.2131	$111.21	$111.20	$111.20
Purchase #2	$80.26	8.133%	$86.7875	$86.79	$86.80	$86.80
Purchase #3	$215.83	3.498%	$223.3797	$223.38	$223.40	$223.40
Purchase #4	$218.88	11.594%	$244.2569	$244.26	$244.25	$244.30
Purchase #5	$77.42	7.696%	$83.3782	$83.38	$83.40	$83.40
Purchase #6	$37.43	5.521%	$39.4965	$39.50	$39.50	$39.50
Purchase #7	$151.38	11.764%	$169.1883	$169.19	$169.20	$169.20
7 purchase totals =	$884.96		$957.7002	$957.71	$957.75	$957.80