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	$67.52	7.375%	$72.4996	$72.50	$72.50	$72.50
Purchase #2	$115.61	9.694%	$126.8172	$126.82	$126.80	$126.80
Purchase #3	$92.72	12.684%	$104.4806	$104.48	$104.50	$104.50
Purchase #4	$21.95	13.749%	$24.9679	$24.97	$24.95	$25.00
Purchase #5	$182.52	12.799%	$205.8807	$205.88	$205.90	$205.90
Purchase #6	$236.25	3.846%	$245.3362	$245.34	$245.35	$245.30
Purchase #7	$209.67	11.414%	$233.6017	$233.60	$233.60	$233.60
7 purchase totals =	$926.24		$1,013.5839	$1,013.59	$1,013.60	$1,013.60