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	$41.30	10.810%	$45.7645	$45.76	$45.75	$45.80
Purchase #2	$178.68	8.512%	$193.8892	$193.89	$193.90	$193.90
Purchase #3	$126.28	10.141%	$139.0861	$139.09	$139.10	$139.10
Purchase #4	$220.97	11.173%	$245.659	$245.66	$245.65	$245.70
Purchase #5	$186.43	10.850%	$206.6577	$206.66	$206.65	$206.70
Purchase #6	$20.57	6.377%	$21.8817	$21.88	$21.90	$21.90
Purchase #7	$182.86	7.653%	$196.8543	$196.85	$196.85	$196.90
7 purchase totals =	$957.09		$1,049.7925	$1,049.79	$1,049.80	$1,050.00