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	$140.60	9.198%	$153.5324	$153.53	$153.55	$153.50
Purchase #2	$85.79	11.780%	$95.8961	$95.90	$95.90	$95.90
Purchase #3	$232.95	11.388%	$259.4783	$259.48	$259.50	$259.50
Purchase #4	$65.77	9.126%	$71.7722	$71.77	$71.75	$71.80
Purchase #5	$185.33	6.150%	$196.7278	$196.73	$196.75	$196.70
Purchase #6	$71.96	9.803%	$79.0142	$79.01	$79.00	$79.00
Purchase #7	$247.48	11.455%	$275.8288	$275.83	$275.85	$275.80
7 purchase totals =	$1,029.88		$1,132.2498	$1,132.25	$1,132.30	$1,132.20