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	$97.71	7.281%	$104.8243	$104.82	$104.80	$104.80
Purchase #2	$111.52	12.804%	$125.799	$125.80	$125.80	$125.80
Purchase #3	$228.95	10.657%	$253.3492	$253.35	$253.35	$253.30
Purchase #4	$76.57	7.820%	$82.5578	$82.56	$82.55	$82.60
Purchase #5	$233.46	3.487%	$241.6008	$241.60	$241.60	$241.60
Purchase #6	$87.90	7.404%	$94.4081	$94.41	$94.40	$94.40
Purchase #7	$211.28	6.534%	$225.085	$225.09	$225.10	$225.10
7 purchase totals =	$1,047.39		$1,127.6242	$1,127.63	$1,127.60	$1,127.60