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	$107.82	4.679%	$112.8649	$112.86	$112.85	$112.90
Purchase #2	$94.53	12.783%	$106.6138	$106.61	$106.60	$106.60
Purchase #3	$244.97	4.476%	$255.9349	$255.93	$255.95	$255.90
Purchase #4	$80.80	5.283%	$85.0687	$85.07	$85.05	$85.10
Purchase #5	$80.88	10.556%	$89.4177	$89.42	$89.40	$89.40
Purchase #6	$66.60	3.325%	$68.8145	$68.81	$68.80	$68.80
Purchase #7	$118.73	12.762%	$133.8823	$133.88	$133.90	$133.90
7 purchase totals =	$794.33		$852.5968	$852.58	$852.55	$852.60