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	$149.56	11.546%	$166.8282	$166.83	$166.85	$166.80
Purchase #2	$35.57	10.692%	$39.3731	$39.37	$39.35	$39.40
Purchase #3	$37.90	4.791%	$39.7158	$39.72	$39.70	$39.70
Purchase #4	$197.87	7.120%	$211.9583	$211.96	$211.95	$212.00
Purchase #5	$164.66	5.191%	$173.2075	$173.21	$173.20	$173.20
Purchase #6	$33.31	13.705%	$37.8751	$37.88	$37.90	$37.90
Purchase #7	$146.38	7.237%	$156.9735	$156.97	$156.95	$157.00
7 purchase totals =	$765.25		$825.9315	$825.94	$825.90	$826.00