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	$140.73	7.657%	$151.5057	$151.51	$151.50	$151.50
Purchase #2	$130.97	9.868%	$143.8941	$143.89	$143.90	$143.90
Purchase #3	$234.59	5.268%	$246.9482	$246.95	$246.95	$246.90
Purchase #4	$192.56	9.698%	$211.2345	$211.23	$211.25	$211.20
Purchase #5	$213.56	13.145%	$241.6325	$241.63	$241.65	$241.60
Purchase #6	$193.99	3.297%	$200.3859	$200.39	$200.40	$200.40
Purchase #7	$109.37	3.219%	$112.8906	$112.89	$112.90	$112.90
7 purchase totals =	$1,215.77		$1,308.4915	$1,308.49	$1,308.55	$1,308.40