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	$168.44	4.296%	$175.6762	$175.68	$175.70	$175.70
Purchase #2	$68.33	3.477%	$70.7058	$70.71	$70.70	$70.70
Purchase #3	$244.75	10.682%	$270.8942	$270.89	$270.90	$270.90
Purchase #4	$81.63	4.167%	$85.0315	$85.03	$85.05	$85.00
Purchase #5	$50.86	5.191%	$53.5001	$53.50	$53.50	$53.50
Purchase #6	$199.52	5.640%	$210.7729	$210.77	$210.75	$210.80
Purchase #7	$44.90	7.584%	$48.3052	$48.31	$48.30	$48.30
7 purchase totals =	$858.43		$914.8859	$914.89	$914.90	$914.90