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	$131.40	4.510%	$137.3261	$137.33	$137.35	$137.30
Purchase #2	$178.62	4.607%	$186.849	$186.85	$186.85	$186.80
Purchase #3	$177.58	7.354%	$190.6392	$190.64	$190.65	$190.60
Purchase #4	$90.29	7.854%	$97.3814	$97.38	$97.40	$97.40
Purchase #5	$90.70	5.152%	$95.3729	$95.37	$95.35	$95.40
Purchase #6	$203.61	9.191%	$222.3238	$222.32	$222.30	$222.30
Purchase #7	$141.33	5.741%	$149.4438	$149.44	$149.45	$149.40
7 purchase totals =	$1,013.53		$1,079.3362	$1,079.33	$1,079.35	$1,079.20