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	$168.47	11.802%	$188.3528	$188.35	$188.35	$188.40
Purchase #2	$180.79	5.407%	$190.5653	$190.57	$190.55	$190.60
Purchase #3	$70.82	7.556%	$76.1712	$76.17	$76.15	$76.20
Purchase #4	$65.57	5.644%	$69.2708	$69.27	$69.25	$69.30
Purchase #5	$42.92	8.787%	$46.6914	$46.69	$46.70	$46.70
Purchase #6	$203.54	7.783%	$219.3815	$219.38	$219.40	$219.40
Purchase #7	$100.27	11.373%	$111.6737	$111.67	$111.65	$111.70
7 purchase totals =	$832.38		$902.1067	$902.10	$902.05	$902.30