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	$250.85	4.567%	$262.3063	$262.31	$262.30	$262.30
Purchase #2	$161.80	4.210%	$168.6118	$168.61	$168.60	$168.60
Purchase #3	$130.56	11.224%	$145.2141	$145.21	$145.20	$145.20
Purchase #4	$105.67	13.679%	$120.1246	$120.12	$120.10	$120.10
Purchase #5	$57.31	11.682%	$64.005	$64.01	$64.00	$64.00
Purchase #6	$37.93	11.543%	$42.3083	$42.31	$42.30	$42.30
Purchase #7	$220.94	12.169%	$247.8262	$247.83	$247.85	$247.80
7 purchase totals =	$965.06		$1,050.3963	$1,050.40	$1,050.35	$1,050.30