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	$192.97	11.360%	$214.8914	$214.89	$214.90	$214.90
Purchase #2	$186.55	9.438%	$204.1566	$204.16	$204.15	$204.20
Purchase #3	$177.73	10.523%	$196.4325	$196.43	$196.45	$196.40
Purchase #4	$157.39	13.790%	$179.0941	$179.09	$179.10	$179.10
Purchase #5	$130.32	12.366%	$146.4354	$146.44	$146.45	$146.40
Purchase #6	$87.32	10.517%	$96.5034	$96.50	$96.50	$96.50
Purchase #7	$80.50	13.120%	$91.0616	$91.06	$91.05	$91.10
7 purchase totals =	$1,012.78		$1,128.5750	$1,128.57	$1,128.60	$1,128.60