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	$118.62	8.717%	$128.9601	$128.96	$128.95	$129.00
Purchase #2	$156.67	6.813%	$167.3439	$167.34	$167.35	$167.30
Purchase #3	$19.72	3.120%	$20.3353	$20.34	$20.35	$20.30
Purchase #4	$12.98	5.375%	$13.6777	$13.68	$13.70	$13.70
Purchase #5	$7.32	6.509%	$7.7965	$7.80	$7.80	$7.80
Purchase #6	$37.59	11.704%	$41.9895	$41.99	$42.00	$42.00
Purchase #7	$33.25	12.310%	$37.3431	$37.34	$37.35	$37.30
7 purchase totals =	$386.15		$417.4461	$417.45	$417.50	$417.40