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	$229.52	11.551%	$256.0319	$256.03	$256.05	$256.00
Purchase #2	$241.54	6.371%	$256.9285	$256.93	$256.95	$256.90
Purchase #3	$54.76	11.667%	$61.1488	$61.15	$61.15	$61.10
Purchase #4	$96.79	11.678%	$108.0931	$108.09	$108.10	$108.10
Purchase #5	$48.31	10.265%	$53.269	$53.27	$53.25	$53.30
Purchase #6	$211.42	5.459%	$222.9614	$222.96	$222.95	$223.00
Purchase #7	$248.28	6.495%	$264.4058	$264.41	$264.40	$264.40
7 purchase totals =	$1,130.62		$1,222.8385	$1,222.84	$1,222.85	$1,222.80