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	$211.66	12.852%	$238.8625	$238.86	$238.85	$238.90
Purchase #2	$44.67	6.213%	$47.4453	$47.45	$47.45	$47.40
Purchase #3	$199.54	10.406%	$220.3041	$220.30	$220.30	$220.30
Purchase #4	$152.87	12.829%	$172.4817	$172.48	$172.50	$172.50
Purchase #5	$13.65	12.592%	$15.3688	$15.37	$15.35	$15.40
Purchase #6	$112.57	12.293%	$126.4082	$126.41	$126.40	$126.40
Purchase #7	$57.55	13.546%	$65.3457	$65.35	$65.35	$65.30
7 purchase totals =	$792.51		$886.2163	$886.22	$886.20	$886.20