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	$190.97	11.483%	$212.8991	$212.90	$212.90	$212.90
Purchase #2	$40.91	4.722%	$42.8418	$42.84	$42.85	$42.80
Purchase #3	$85.90	5.276%	$90.4321	$90.43	$90.45	$90.40
Purchase #4	$225.82	4.266%	$235.4535	$235.45	$235.45	$235.50
Purchase #5	$146.68	3.283%	$151.4955	$151.50	$151.50	$151.50
Purchase #6	$202.48	13.104%	$229.013	$229.01	$229.00	$229.00
Purchase #7	$156.97	12.204%	$176.1266	$176.13	$176.15	$176.10
7 purchase totals =	$1,049.73		$1,138.2616	$1,138.26	$1,138.30	$1,138.20