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	$142.63	12.121%	$159.9182	$159.92	$159.90	$159.90
Purchase #2	$134.28	5.113%	$141.1457	$141.15	$141.15	$141.10
Purchase #3	$150.88	9.218%	$164.7881	$164.79	$164.80	$164.80
Purchase #4	$150.95	12.110%	$169.23	$169.23	$169.25	$169.20
Purchase #5	$167.69	13.598%	$190.4925	$190.49	$190.50	$190.50
Purchase #6	$67.49	3.308%	$69.7226	$69.72	$69.70	$69.70
Purchase #7	$35.59	5.858%	$37.6749	$37.67	$37.65	$37.70
7 purchase totals =	$849.51		$932.9720	$932.97	$932.95	$932.90