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	$169.26	12.767%	$190.8694	$190.87	$190.85	$190.90
Purchase #2	$153.45	13.686%	$174.4512	$174.45	$174.45	$174.50
Purchase #3	$190.31	12.406%	$213.9199	$213.92	$213.90	$213.90
Purchase #4	$86.94	12.613%	$97.9057	$97.91	$97.90	$97.90
Purchase #5	$88.70	12.297%	$99.6074	$99.61	$99.60	$99.60
Purchase #6	$10.28	4.711%	$10.7643	$10.76	$10.75	$10.80
Purchase #7	$177.28	3.401%	$183.3093	$183.31	$183.30	$183.30
7 purchase totals =	$876.22		$970.8272	$970.83	$970.75	$970.90