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	$98.64	10.389%	$108.8877	$108.89	$108.90	$108.90
Purchase #2	$78.50	4.778%	$82.2507	$82.25	$82.25	$82.30
Purchase #3	$136.29	4.723%	$142.727	$142.73	$142.75	$142.70
Purchase #4	$77.54	12.829%	$87.4876	$87.49	$87.50	$87.50
Purchase #5	$194.40	8.575%	$211.0698	$211.07	$211.05	$211.10
Purchase #6	$191.28	10.584%	$211.5251	$211.53	$211.55	$211.50
Purchase #7	$112.74	11.420%	$125.6149	$125.61	$125.60	$125.60
7 purchase totals =	$889.39		$969.5628	$969.57	$969.60	$969.60