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	$184.90	3.256%	$190.9203	$190.92	$190.90	$190.90
Purchase #2	$91.73	3.624%	$95.0543	$95.05	$95.05	$95.10
Purchase #3	$110.25	4.762%	$115.5001	$115.50	$115.50	$115.50
Purchase #4	$99.62	4.343%	$103.9465	$103.95	$103.95	$103.90
Purchase #5	$99.42	3.465%	$102.8649	$102.86	$102.85	$102.90
Purchase #6	$83.32	7.587%	$89.6415	$89.64	$89.65	$89.60
Purchase #7	$37.77	13.340%	$42.8085	$42.81	$42.80	$42.80
7 purchase totals =	$707.01		$740.7361	$740.73	$740.70	$740.70