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	$221.49	7.118%	$237.2557	$237.26	$237.25	$237.30
Purchase #2	$171.42	8.688%	$186.313	$186.31	$186.30	$186.30
Purchase #3	$22.74	12.225%	$25.52	$25.52	$25.50	$25.50
Purchase #4	$244.96	7.726%	$263.8856	$263.89	$263.90	$263.90
Purchase #5	$126.50	8.834%	$137.675	$137.68	$137.70	$137.70
Purchase #6	$112.32	12.312%	$126.1488	$126.15	$126.15	$126.10
Purchase #7	$78.63	13.840%	$89.5124	$89.51	$89.50	$89.50
7 purchase totals =	$978.06		$1,066.3105	$1,066.32	$1,066.30	$1,066.30