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	$188.97	12.364%	$212.3343	$212.33	$212.35	$212.30
Purchase #2	$33.72	12.427%	$37.9104	$37.91	$37.90	$37.90
Purchase #3	$199.84	12.305%	$224.4303	$224.43	$224.45	$224.40
Purchase #4	$75.89	3.485%	$78.5348	$78.53	$78.55	$78.50
Purchase #5	$141.33	13.371%	$160.2272	$160.23	$160.25	$160.20
Purchase #6	$210.64	3.416%	$217.8355	$217.84	$217.85	$217.80
Purchase #7	$49.72	6.341%	$52.8727	$52.87	$52.85	$52.90
7 purchase totals =	$900.11		$984.1452	$984.14	$984.20	$984.00