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	$116.40	12.825%	$131.3283	$131.33	$131.35	$131.30
Purchase #2	$135.89	9.256%	$148.468	$148.47	$148.45	$148.50
Purchase #3	$238.66	9.242%	$260.717	$260.72	$260.70	$260.70
Purchase #4	$197.65	13.527%	$224.3861	$224.39	$224.40	$224.40
Purchase #5	$246.76	9.659%	$270.5945	$270.59	$270.60	$270.60
Purchase #6	$157.98	4.699%	$165.4035	$165.40	$165.40	$165.40
Purchase #7	$51.46	4.208%	$53.6254	$53.63	$53.65	$53.60
7 purchase totals =	$1,144.80		$1,254.5228	$1,254.53	$1,254.55	$1,254.50