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	$39.89	6.163%	$42.3484	$42.35	$42.35	$42.30
Purchase #2	$171.42	12.150%	$192.2475	$192.25	$192.25	$192.20
Purchase #3	$136.44	3.145%	$140.731	$140.73	$140.75	$140.70
Purchase #4	$228.56	5.817%	$241.8553	$241.86	$241.85	$241.90
Purchase #5	$200.81	6.679%	$214.2221	$214.22	$214.20	$214.20
Purchase #6	$71.72	13.278%	$81.243	$81.24	$81.25	$81.20
Purchase #7	$176.70	3.768%	$183.3581	$183.36	$183.35	$183.40
7 purchase totals =	$1,025.54		$1,096.0054	$1,096.01	$1,096.00	$1,095.90