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	$140.86	10.531%	$155.694	$155.69	$155.70	$155.70
Purchase #2	$178.33	4.209%	$185.8359	$185.84	$185.85	$185.80
Purchase #3	$225.98	5.244%	$237.8304	$237.83	$237.85	$237.80
Purchase #4	$150.51	6.646%	$160.5129	$160.51	$160.50	$160.50
Purchase #5	$85.47	7.599%	$91.9649	$91.96	$91.95	$92.00
Purchase #6	$195.79	11.128%	$217.5775	$217.58	$217.60	$217.60
Purchase #7	$166.59	7.515%	$179.1092	$179.11	$179.10	$179.10
7 purchase totals =	$1,143.53		$1,228.5248	$1,228.52	$1,228.55	$1,228.50