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	$229.75	10.663%	$254.2482	$254.25	$254.25	$254.20
Purchase #2	$185.64	12.638%	$209.1012	$209.10	$209.10	$209.10
Purchase #3	$106.41	5.198%	$111.9412	$111.94	$111.95	$111.90
Purchase #4	$64.72	4.368%	$67.547	$67.55	$67.55	$67.50
Purchase #5	$218.38	10.441%	$241.1811	$241.18	$241.20	$241.20
Purchase #6	$185.72	13.562%	$210.9073	$210.91	$210.90	$210.90
Purchase #7	$191.98	10.456%	$212.0534	$212.05	$212.05	$212.10
7 purchase totals =	$1,182.60		$1,306.9794	$1,306.98	$1,307.00	$1,306.90