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	$69.99	4.367%	$73.0465	$73.05	$73.05	$73.00
Purchase #2	$33.61	5.545%	$35.4737	$35.47	$35.45	$35.50
Purchase #3	$53.84	6.715%	$57.4554	$57.46	$57.45	$57.50
Purchase #4	$59.39	13.104%	$67.1725	$67.17	$67.15	$67.20
Purchase #5	$184.42	8.181%	$199.5074	$199.51	$199.50	$199.50
Purchase #6	$156.27	5.562%	$164.9617	$164.96	$164.95	$165.00
Purchase #7	$98.49	7.554%	$105.9299	$105.93	$105.95	$105.90
7 purchase totals =	$656.01		$703.5471	$703.55	$703.50	$703.60