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	$193.40	11.201%	$215.0627	$215.06	$215.05	$215.10
Purchase #2	$148.60	8.108%	$160.6485	$160.65	$160.65	$160.60
Purchase #3	$32.42	11.615%	$36.1856	$36.19	$36.20	$36.20
Purchase #4	$142.79	6.266%	$151.7372	$151.74	$151.75	$151.70
Purchase #5	$241.59	9.463%	$264.4517	$264.45	$264.45	$264.50
Purchase #6	$73.38	12.496%	$82.5496	$82.55	$82.55	$82.50
Purchase #7	$120.66	13.497%	$136.9455	$136.95	$136.95	$136.90
7 purchase totals =	$952.84		$1,047.5808	$1,047.59	$1,047.60	$1,047.50