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	$119.82	8.728%	$130.2779	$130.28	$130.30	$130.30
Purchase #2	$41.73	5.247%	$43.9196	$43.92	$43.90	$43.90
Purchase #3	$120.40	3.863%	$125.0511	$125.05	$125.05	$125.10
Purchase #4	$43.25	7.301%	$46.4077	$46.41	$46.40	$46.40
Purchase #5	$183.70	8.581%	$199.4633	$199.46	$199.45	$199.50
Purchase #6	$35.59	4.818%	$37.3047	$37.30	$37.30	$37.30
Purchase #7	$155.84	10.650%	$172.437	$172.44	$172.45	$172.40
7 purchase totals =	$700.33		$754.8613	$754.86	$754.85	$754.90