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	$61.25	4.398%	$63.9438	$63.94	$63.95	$63.90
Purchase #2	$60.37	9.459%	$66.0804	$66.08	$66.10	$66.10
Purchase #3	$228.74	9.685%	$250.8935	$250.89	$250.90	$250.90
Purchase #4	$228.57	4.194%	$238.1562	$238.16	$238.15	$238.20
Purchase #5	$189.88	11.257%	$211.2548	$211.25	$211.25	$211.30
Purchase #6	$95.76	9.417%	$104.7777	$104.78	$104.80	$104.80
Purchase #7	$56.89	11.210%	$63.2674	$63.27	$63.25	$63.30
7 purchase totals =	$921.46		$998.3738	$998.37	$998.40	$998.50