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	$169.89	10.156%	$187.144	$187.14	$187.15	$187.10
Purchase #2	$133.54	11.311%	$148.6447	$148.64	$148.65	$148.60
Purchase #3	$172.65	5.818%	$182.6948	$182.69	$182.70	$182.70
Purchase #4	$14.78	7.654%	$15.9113	$15.91	$15.90	$15.90
Purchase #5	$208.34	5.294%	$219.3695	$219.37	$219.35	$219.40
Purchase #6	$223.96	6.385%	$238.2598	$238.26	$238.25	$238.30
Purchase #7	$71.94	6.377%	$76.5276	$76.53	$76.55	$76.50
7 purchase totals =	$995.10		$1,068.5517	$1,068.54	$1,068.55	$1,068.50