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	$110.46	11.717%	$123.4026	$123.40	$123.40	$123.40
Purchase #2	$128.63	3.793%	$133.5089	$133.51	$133.50	$133.50
Purchase #3	$154.72	4.643%	$161.9036	$161.90	$161.90	$161.90
Purchase #4	$96.63	3.381%	$99.8971	$99.90	$99.90	$99.90
Purchase #5	$188.90	10.381%	$208.5097	$208.51	$208.50	$208.50
Purchase #6	$177.72	8.749%	$193.2687	$193.27	$193.25	$193.30
Purchase #7	$25.86	8.189%	$27.9777	$27.98	$28.00	$28.00
7 purchase totals =	$882.92		$948.4683	$948.47	$948.45	$948.50