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	$121.65	10.543%	$134.4756	$134.48	$134.50	$134.50
Purchase #2	$69.41	3.684%	$71.9671	$71.97	$71.95	$72.00
Purchase #3	$40.35	11.830%	$45.1234	$45.12	$45.10	$45.10
Purchase #4	$176.46	10.819%	$195.5512	$195.55	$195.55	$195.60
Purchase #5	$134.83	13.358%	$152.8406	$152.84	$152.85	$152.80
Purchase #6	$181.48	9.837%	$199.3322	$199.33	$199.35	$199.30
Purchase #7	$43.55	4.175%	$45.3682	$45.37	$45.35	$45.40
7 purchase totals =	$767.73		$844.6583	$844.66	$844.65	$844.70