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	$152.91	3.482%	$158.2343	$158.23	$158.25	$158.20
Purchase #2	$133.44	3.504%	$138.1157	$138.12	$138.10	$138.10
Purchase #3	$145.84	5.837%	$154.3527	$154.35	$154.35	$154.40
Purchase #4	$75.94	9.229%	$82.9485	$82.95	$82.95	$82.90
Purchase #5	$231.50	13.588%	$262.9562	$262.96	$262.95	$263.00
Purchase #6	$237.54	9.103%	$259.1633	$259.16	$259.15	$259.20
Purchase #7	$42.31	12.406%	$47.559	$47.56	$47.55	$47.60
7 purchase totals =	$1,019.48		$1,103.3297	$1,103.33	$1,103.30	$1,103.40