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	$241.25	5.470%	$254.4464	$254.45	$254.45	$254.40
Purchase #2	$213.76	6.456%	$227.5603	$227.56	$227.55	$227.60
Purchase #3	$132.29	4.483%	$138.2206	$138.22	$138.20	$138.20
Purchase #4	$38.56	13.300%	$43.6885	$43.69	$43.70	$43.70
Purchase #5	$26.76	11.579%	$29.8585	$29.86	$29.85	$29.90
Purchase #6	$223.63	11.837%	$250.1011	$250.10	$250.10	$250.10
Purchase #7	$144.52	11.740%	$161.4866	$161.49	$161.50	$161.50
7 purchase totals =	$1,020.77		$1,105.3620	$1,105.37	$1,105.35	$1,105.40