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	$164.61	9.574%	$180.3698	$180.37	$180.35	$180.40
Purchase #2	$234.27	3.421%	$242.2844	$242.28	$242.30	$242.30
Purchase #3	$171.63	10.402%	$189.483	$189.48	$189.50	$189.50
Purchase #4	$59.33	4.213%	$61.8296	$61.83	$61.85	$61.80
Purchase #5	$113.52	6.651%	$121.0702	$121.07	$121.05	$121.10
Purchase #6	$217.60	13.644%	$247.2893	$247.29	$247.30	$247.30
Purchase #7	$52.25	13.456%	$59.2808	$59.28	$59.30	$59.30
7 purchase totals =	$1,013.21		$1,101.6071	$1,101.60	$1,101.65	$1,101.70