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	$190.51	13.295%	$215.8383	$215.84	$215.85	$215.80
Purchase #2	$80.53	12.635%	$90.705	$90.71	$90.70	$90.70
Purchase #3	$160.94	4.261%	$167.7977	$167.80	$167.80	$167.80
Purchase #4	$232.93	3.598%	$241.3108	$241.31	$241.30	$241.30
Purchase #5	$9.84	4.774%	$10.3098	$10.31	$10.30	$10.30
Purchase #6	$81.34	9.659%	$89.1966	$89.20	$89.20	$89.20
Purchase #7	$70.39	9.571%	$77.127	$77.13	$77.15	$77.10
7 purchase totals =	$826.48		$892.2852	$892.30	$892.30	$892.20