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	$72.73	7.873%	$78.456	$78.46	$78.45	$78.50
Purchase #2	$77.42	10.405%	$85.4756	$85.48	$85.50	$85.50
Purchase #3	$229.72	5.741%	$242.9082	$242.91	$242.90	$242.90
Purchase #4	$5.71	4.186%	$5.949	$5.95	$5.95	$5.90
Purchase #5	$33.65	13.557%	$38.2119	$38.21	$38.20	$38.20
Purchase #6	$190.34	13.738%	$216.4889	$216.49	$216.50	$216.50
Purchase #7	$189.81	9.710%	$208.2406	$208.24	$208.25	$208.20
7 purchase totals =	$799.38		$875.7302	$875.74	$875.75	$875.70