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	$167.60	10.592%	$185.3522	$185.35	$185.35	$185.40
Purchase #2	$167.82	4.627%	$175.585	$175.59	$175.60	$175.60
Purchase #3	$165.34	6.110%	$175.4423	$175.44	$175.45	$175.40
Purchase #4	$61.59	6.500%	$65.5934	$65.59	$65.60	$65.60
Purchase #5	$181.51	12.219%	$203.6887	$203.69	$203.70	$203.70
Purchase #6	$122.65	7.517%	$131.8696	$131.87	$131.85	$131.90
Purchase #7	$222.99	10.133%	$245.5856	$245.59	$245.60	$245.60
7 purchase totals =	$1,089.50		$1,183.1168	$1,183.12	$1,183.15	$1,183.20