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	$50.56	8.279%	$54.7459	$54.75	$54.75	$54.70
Purchase #2	$90.57	6.221%	$96.2044	$96.20	$96.20	$96.20
Purchase #3	$214.76	10.111%	$236.4744	$236.47	$236.45	$236.50
Purchase #4	$73.73	4.601%	$77.1223	$77.12	$77.10	$77.10
Purchase #5	$208.75	6.468%	$222.252	$222.25	$222.25	$222.30
Purchase #6	$127.86	11.778%	$142.9194	$142.92	$142.90	$142.90
Purchase #7	$95.88	8.739%	$104.259	$104.26	$104.25	$104.30
7 purchase totals =	$862.11		$933.9774	$933.97	$933.90	$934.00