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	$129.61	11.641%	$144.6979	$144.70	$144.70	$144.70
Purchase #2	$136.89	13.624%	$155.5399	$155.54	$155.55	$155.50
Purchase #3	$19.50	4.491%	$20.3757	$20.38	$20.40	$20.40
Purchase #4	$73.32	7.628%	$78.9128	$78.91	$78.90	$78.90
Purchase #5	$119.97	3.816%	$124.5481	$124.55	$124.55	$124.50
Purchase #6	$97.47	4.365%	$101.7246	$101.72	$101.70	$101.70
Purchase #7	$160.81	8.764%	$174.9034	$174.90	$174.90	$174.90
7 purchase totals =	$737.57		$800.7024	$800.70	$800.70	$800.60