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	$64.58	8.873%	$70.3102	$70.31	$70.30	$70.30
Purchase #2	$227.68	7.576%	$244.929	$244.93	$244.95	$244.90
Purchase #3	$243.74	5.518%	$257.1896	$257.19	$257.20	$257.20
Purchase #4	$92.59	12.522%	$104.1841	$104.18	$104.20	$104.20
Purchase #5	$189.80	5.836%	$200.8767	$200.88	$200.90	$200.90
Purchase #6	$103.79	7.408%	$111.4788	$111.48	$111.50	$111.50
Purchase #7	$41.58	7.122%	$44.5413	$44.54	$44.55	$44.50
7 purchase totals =	$963.76		$1,033.5097	$1,033.51	$1,033.60	$1,033.50