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	$95.81	12.450%	$107.7383	$107.74	$107.75	$107.70
Purchase #2	$99.45	12.446%	$111.8275	$111.83	$111.85	$111.80
Purchase #3	$82.83	6.818%	$88.4773	$88.48	$88.50	$88.50
Purchase #4	$52.61	13.823%	$59.8823	$59.88	$59.90	$59.90
Purchase #5	$214.61	5.804%	$227.066	$227.07	$227.05	$227.10
Purchase #6	$100.67	6.387%	$107.0998	$107.10	$107.10	$107.10
Purchase #7	$123.33	5.854%	$130.5497	$130.55	$130.55	$130.50
7 purchase totals =	$769.31		$832.6409	$832.65	$832.70	$832.60