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	$86.53	6.408%	$92.0748	$92.07	$92.05	$92.10
Purchase #2	$230.86	11.283%	$256.9079	$256.91	$256.90	$256.90
Purchase #3	$222.43	11.860%	$248.8102	$248.81	$248.80	$248.80
Purchase #4	$33.48	12.739%	$37.745	$37.75	$37.75	$37.70
Purchase #5	$218.28	10.517%	$241.2365	$241.24	$241.25	$241.20
Purchase #6	$196.70	9.502%	$215.3904	$215.39	$215.40	$215.40
Purchase #7	$127.82	7.831%	$137.8296	$137.83	$137.85	$137.80
7 purchase totals =	$1,116.10		$1,229.9944	$1,230.00	$1,230.00	$1,229.90