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	$86.46	8.178%	$93.5307	$93.53	$93.55	$93.50
Purchase #2	$137.26	11.579%	$153.1533	$153.15	$153.15	$153.20
Purchase #3	$83.52	8.440%	$90.5691	$90.57	$90.55	$90.60
Purchase #4	$50.38	6.284%	$53.5459	$53.55	$53.55	$53.50
Purchase #5	$169.74	3.396%	$175.5044	$175.50	$175.50	$175.50
Purchase #6	$41.86	6.402%	$44.5399	$44.54	$44.55	$44.50
Purchase #7	$233.73	12.108%	$262.03	$262.03	$262.05	$262.00
7 purchase totals =	$802.95		$872.8733	$872.87	$872.90	$872.80