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	$238.33	7.188%	$255.4612	$255.46	$255.45	$255.50
Purchase #2	$211.70	5.664%	$223.6907	$223.69	$223.70	$223.70
Purchase #3	$168.90	7.383%	$181.3699	$181.37	$181.35	$181.40
Purchase #4	$229.51	4.611%	$240.0927	$240.09	$240.10	$240.10
Purchase #5	$158.43	8.323%	$171.6161	$171.62	$171.60	$171.60
Purchase #6	$64.55	11.453%	$71.9429	$71.94	$71.95	$71.90
Purchase #7	$118.46	6.555%	$126.2251	$126.23	$126.25	$126.20
7 purchase totals =	$1,189.88		$1,270.3986	$1,270.40	$1,270.40	$1,270.40