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	$107.84	3.427%	$111.5357	$111.54	$111.55	$111.50
Purchase #2	$131.85	9.783%	$144.7489	$144.75	$144.75	$144.70
Purchase #3	$6.58	6.196%	$6.9877	$6.99	$7.00	$7.00
Purchase #4	$158.49	9.412%	$173.4071	$173.41	$173.40	$173.40
Purchase #5	$63.63	12.604%	$71.6499	$71.65	$71.65	$71.60
Purchase #6	$88.55	11.311%	$98.5659	$98.57	$98.55	$98.60
Purchase #7	$134.86	12.180%	$151.2859	$151.29	$151.30	$151.30
7 purchase totals =	$691.80		$758.1811	$758.20	$758.20	$758.10