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	$186.25	4.651%	$194.9125	$194.91	$194.90	$194.90
Purchase #2	$41.57	3.640%	$43.0831	$43.08	$43.10	$43.10
Purchase #3	$60.57	11.386%	$67.4665	$67.47	$67.45	$67.50
Purchase #4	$190.61	5.223%	$200.5656	$200.57	$200.55	$200.60
Purchase #5	$226.55	13.363%	$256.8239	$256.82	$256.80	$256.80
Purchase #6	$149.50	12.513%	$168.2069	$168.21	$168.20	$168.20
Purchase #7	$70.94	7.155%	$76.0158	$76.02	$76.00	$76.00
7 purchase totals =	$925.99		$1,007.0743	$1,007.08	$1,007.00	$1,007.10