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	$143.58	5.502%	$151.4798	$151.48	$151.50	$151.50
Purchase #2	$176.64	13.443%	$200.3857	$200.39	$200.40	$200.40
Purchase #3	$186.82	4.806%	$195.7986	$195.80	$195.80	$195.80
Purchase #4	$118.38	7.873%	$127.7001	$127.70	$127.70	$127.70
Purchase #5	$178.72	11.565%	$199.389	$199.39	$199.40	$199.40
Purchase #6	$24.80	5.769%	$26.2307	$26.23	$26.25	$26.20
Purchase #7	$85.72	11.864%	$95.8898	$95.89	$95.90	$95.90
7 purchase totals =	$914.66		$996.8737	$996.88	$996.95	$996.90