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	$83.90	11.472%	$93.525	$93.53	$93.55	$93.50
Purchase #2	$50.35	8.674%	$54.7174	$54.72	$54.70	$54.70
Purchase #3	$12.31	6.798%	$13.1468	$13.15	$13.15	$13.10
Purchase #4	$89.41	3.379%	$92.4312	$92.43	$92.45	$92.40
Purchase #5	$213.53	4.629%	$223.4143	$223.41	$223.40	$223.40
Purchase #6	$245.66	7.660%	$264.4776	$264.48	$264.50	$264.50
Purchase #7	$204.78	13.842%	$233.1256	$233.13	$233.15	$233.10
7 purchase totals =	$899.94		$974.8379	$974.85	$974.90	$974.70