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	$43.80	3.194%	$45.199	$45.20	$45.20	$45.20
Purchase #2	$172.55	10.354%	$190.4158	$190.42	$190.40	$190.40
Purchase #3	$22.27	10.772%	$24.6689	$24.67	$24.65	$24.70
Purchase #4	$235.59	9.845%	$258.7838	$258.78	$258.80	$258.80
Purchase #5	$221.89	3.412%	$229.4609	$229.46	$229.45	$229.50
Purchase #6	$29.67	6.372%	$31.5606	$31.56	$31.55	$31.60
Purchase #7	$243.72	8.375%	$264.1316	$264.13	$264.15	$264.10
7 purchase totals =	$969.49		$1,044.2206	$1,044.22	$1,044.20	$1,044.30