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	$140.30	10.434%	$154.9389	$154.94	$154.95	$154.90
Purchase #2	$65.51	3.567%	$67.8467	$67.85	$67.85	$67.80
Purchase #3	$221.39	10.647%	$244.9614	$244.96	$244.95	$245.00
Purchase #4	$171.54	12.160%	$192.3993	$192.40	$192.40	$192.40
Purchase #5	$39.60	4.147%	$41.2422	$41.24	$41.25	$41.20
Purchase #6	$229.51	3.294%	$237.0701	$237.07	$237.05	$237.10
Purchase #7	$182.77	5.537%	$192.89	$192.89	$192.90	$192.90
7 purchase totals =	$1,050.62		$1,131.3486	$1,131.35	$1,131.35	$1,131.30