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	$147.46	10.367%	$162.7472	$162.75	$162.75	$162.70
Purchase #2	$210.70	3.407%	$217.8785	$217.88	$217.90	$217.90
Purchase #3	$121.30	13.304%	$137.4378	$137.44	$137.45	$137.40
Purchase #4	$209.52	6.190%	$222.4893	$222.49	$222.50	$222.50
Purchase #5	$15.51	6.660%	$16.543	$16.54	$16.55	$16.50
Purchase #6	$96.58	3.274%	$99.742	$99.74	$99.75	$99.70
Purchase #7	$207.56	7.444%	$223.0108	$223.01	$223.00	$223.00
7 purchase totals =	$1,008.63		$1,079.8486	$1,079.85	$1,079.90	$1,079.70