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	$43.25	5.323%	$45.5522	$45.55	$45.55	$45.60
Purchase #2	$136.45	5.134%	$143.4553	$143.46	$143.45	$143.50
Purchase #3	$172.69	8.806%	$187.8971	$187.90	$187.90	$187.90
Purchase #4	$238.47	13.565%	$270.8185	$270.82	$270.80	$270.80
Purchase #5	$168.98	12.146%	$189.5043	$189.50	$189.50	$189.50
Purchase #6	$234.72	10.815%	$260.105	$260.11	$260.10	$260.10
Purchase #7	$99.90	6.837%	$106.7302	$106.73	$106.75	$106.70
7 purchase totals =	$1,094.46		$1,204.0626	$1,204.07	$1,204.05	$1,204.10