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	$77.25	7.129%	$82.7572	$82.76	$82.75	$82.80
Purchase #2	$65.42	4.768%	$68.5392	$68.54	$68.55	$68.50
Purchase #3	$199.99	8.234%	$216.4572	$216.46	$216.45	$216.50
Purchase #4	$162.90	13.442%	$184.797	$184.80	$184.80	$184.80
Purchase #5	$233.40	11.697%	$260.7008	$260.70	$260.70	$260.70
Purchase #6	$156.29	7.412%	$167.8742	$167.87	$167.85	$167.90
Purchase #7	$134.81	5.776%	$142.5966	$142.60	$142.60	$142.60
7 purchase totals =	$1,030.06		$1,123.7222	$1,123.73	$1,123.70	$1,123.80