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	$126.58	5.638%	$133.7166	$133.72	$133.70	$133.70
Purchase #2	$33.31	11.621%	$37.181	$37.18	$37.20	$37.20
Purchase #3	$33.46	13.119%	$37.8496	$37.85	$37.85	$37.80
Purchase #4	$34.89	10.377%	$38.5105	$38.51	$38.50	$38.50
Purchase #5	$73.58	6.807%	$78.5886	$78.59	$78.60	$78.60
Purchase #6	$121.67	10.577%	$134.539	$134.54	$134.55	$134.50
Purchase #7	$148.33	9.801%	$162.8678	$162.87	$162.85	$162.90
7 purchase totals =	$571.82		$623.2531	$623.26	$623.25	$623.20