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	$172.64	13.866%	$196.5783	$196.58	$196.60	$196.60
Purchase #2	$162.62	12.218%	$182.4889	$182.49	$182.50	$182.50
Purchase #3	$225.38	13.356%	$255.4818	$255.48	$255.50	$255.50
Purchase #4	$121.91	5.298%	$128.3688	$128.37	$128.35	$128.40
Purchase #5	$118.84	9.255%	$129.8386	$129.84	$129.85	$129.80
Purchase #6	$27.73	6.369%	$29.4961	$29.50	$29.50	$29.50
Purchase #7	$209.72	12.461%	$235.8532	$235.85	$235.85	$235.90
7 purchase totals =	$1,038.84		$1,158.1057	$1,158.11	$1,158.15	$1,158.20