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	$238.26	5.689%	$251.8146	$251.81	$251.80	$251.80
Purchase #2	$188.54	8.484%	$204.5357	$204.54	$204.55	$204.50
Purchase #3	$66.39	9.588%	$72.7555	$72.76	$72.75	$72.80
Purchase #4	$208.57	4.471%	$217.8952	$217.90	$217.90	$217.90
Purchase #5	$185.76	13.186%	$210.2543	$210.25	$210.25	$210.30
Purchase #6	$188.97	11.492%	$210.6864	$210.69	$210.70	$210.70
Purchase #7	$83.26	3.213%	$85.9351	$85.94	$85.95	$85.90
7 purchase totals =	$1,159.75		$1,253.8768	$1,253.89	$1,253.90	$1,253.90