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	$139.73	8.726%	$151.9228	$151.92	$151.90	$151.90
Purchase #2	$76.97	8.260%	$83.3277	$83.33	$83.35	$83.30
Purchase #3	$151.87	5.870%	$160.7848	$160.78	$160.80	$160.80
Purchase #4	$88.38	12.141%	$99.1102	$99.11	$99.10	$99.10
Purchase #5	$57.96	6.633%	$61.8045	$61.80	$61.80	$61.80
Purchase #6	$140.25	5.170%	$147.5009	$147.50	$147.50	$147.50
Purchase #7	$145.63	8.137%	$157.4799	$157.48	$157.50	$157.50
7 purchase totals =	$800.79		$861.9308	$861.92	$861.95	$861.90