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	$99.66	6.186%	$105.825	$105.83	$105.85	$105.80
Purchase #2	$175.48	3.874%	$182.2781	$182.28	$182.30	$182.30
Purchase #3	$145.27	3.597%	$150.4954	$150.50	$150.50	$150.50
Purchase #4	$140.98	13.440%	$159.9277	$159.93	$159.95	$159.90
Purchase #5	$89.26	7.308%	$95.7831	$95.78	$95.80	$95.80
Purchase #6	$173.60	13.764%	$197.4943	$197.49	$197.50	$197.50
Purchase #7	$206.56	3.458%	$213.7028	$213.70	$213.70	$213.70
7 purchase totals =	$1,030.81		$1,105.5064	$1,105.51	$1,105.60	$1,105.50