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	$172.44	5.253%	$181.4983	$181.50	$181.50	$181.50
Purchase #2	$26.72	11.237%	$29.7225	$29.72	$29.70	$29.70
Purchase #3	$113.89	12.721%	$128.3779	$128.38	$128.40	$128.40
Purchase #4	$152.98	4.198%	$159.4021	$159.40	$159.40	$159.40
Purchase #5	$65.84	13.744%	$74.889	$74.89	$74.90	$74.90
Purchase #6	$235.61	11.412%	$262.4978	$262.50	$262.50	$262.50
Purchase #7	$152.87	9.421%	$167.2719	$167.27	$167.25	$167.30
7 purchase totals =	$920.35		$1,003.6595	$1,003.66	$1,003.65	$1,003.70