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	$136.83	3.604%	$141.7614	$141.76	$141.75	$141.80
Purchase #2	$81.97	10.358%	$90.4605	$90.46	$90.45	$90.50
Purchase #3	$136.68	11.595%	$152.528	$152.53	$152.55	$152.50
Purchase #4	$144.59	3.841%	$150.1437	$150.14	$150.15	$150.10
Purchase #5	$124.56	13.191%	$140.9907	$140.99	$141.00	$141.00
Purchase #6	$44.38	4.384%	$46.3256	$46.33	$46.35	$46.30
Purchase #7	$48.73	9.204%	$53.2151	$53.22	$53.20	$53.20
7 purchase totals =	$717.74		$775.4250	$775.43	$775.45	$775.40