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	$250.27	4.745%	$262.1453	$262.15	$262.15	$262.10
Purchase #2	$30.27	7.805%	$32.6326	$32.63	$32.65	$32.60
Purchase #3	$136.39	10.299%	$150.4368	$150.44	$150.45	$150.40
Purchase #4	$117.83	13.834%	$134.1306	$134.13	$134.15	$134.10
Purchase #5	$44.83	13.304%	$50.7942	$50.79	$50.80	$50.80
Purchase #6	$125.59	9.464%	$137.4758	$137.48	$137.50	$137.50
Purchase #7	$97.63	7.312%	$104.7687	$104.77	$104.75	$104.80
7 purchase totals =	$802.81		$872.3840	$872.39	$872.45	$872.30