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	$236.33	4.276%	$246.4355	$246.44	$246.45	$246.40
Purchase #2	$175.77	7.104%	$188.2567	$188.26	$188.25	$188.30
Purchase #3	$158.83	8.736%	$172.7054	$172.71	$172.70	$172.70
Purchase #4	$33.68	4.862%	$35.3175	$35.32	$35.30	$35.30
Purchase #5	$114.59	13.833%	$130.4412	$130.44	$130.45	$130.40
Purchase #6	$108.64	13.119%	$122.8925	$122.89	$122.90	$122.90
Purchase #7	$199.29	8.181%	$215.5939	$215.59	$215.60	$215.60
7 purchase totals =	$1,027.13		$1,111.6427	$1,111.65	$1,111.65	$1,111.60