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	$93.29	13.190%	$105.595	$105.60	$105.60	$105.60
Purchase #2	$242.86	11.512%	$270.818	$270.82	$270.80	$270.80
Purchase #3	$88.40	7.546%	$95.0707	$95.07	$95.05	$95.10
Purchase #4	$92.30	4.569%	$96.5172	$96.52	$96.50	$96.50
Purchase #5	$43.93	12.623%	$49.4753	$49.48	$49.50	$49.50
Purchase #6	$147.25	3.468%	$152.3566	$152.36	$152.35	$152.40
Purchase #7	$10.70	8.113%	$11.5681	$11.57	$11.55	$11.60
7 purchase totals =	$718.73		$781.4009	$781.42	$781.35	$781.50