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	$172.85	7.195%	$185.2866	$185.29	$185.30	$185.30
Purchase #2	$45.33	3.363%	$46.8544	$46.85	$46.85	$46.90
Purchase #3	$19.74	10.709%	$21.854	$21.85	$21.85	$21.90
Purchase #4	$103.25	12.419%	$116.0726	$116.07	$116.05	$116.10
Purchase #5	$101.90	4.532%	$106.5181	$106.52	$106.50	$106.50
Purchase #6	$192.60	3.150%	$198.6669	$198.67	$198.65	$198.70
Purchase #7	$89.62	6.680%	$95.6066	$95.61	$95.60	$95.60
7 purchase totals =	$725.29		$770.8592	$770.86	$770.80	$771.00