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	$98.55	12.237%	$110.6096	$110.61	$110.60	$110.60
Purchase #2	$131.58	8.409%	$142.6446	$142.64	$142.65	$142.60
Purchase #3	$83.78	7.770%	$90.2897	$90.29	$90.30	$90.30
Purchase #4	$101.52	8.431%	$110.0792	$110.08	$110.10	$110.10
Purchase #5	$177.34	6.206%	$188.3457	$188.35	$188.35	$188.30
Purchase #6	$29.48	10.428%	$32.5542	$32.55	$32.55	$32.60
Purchase #7	$203.45	12.784%	$229.459	$229.46	$229.45	$229.50
7 purchase totals =	$825.70		$903.9820	$903.98	$904.00	$904.00