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	$213.79	3.833%	$221.9846	$221.98	$222.00	$222.00
Purchase #2	$30.29	6.708%	$32.3219	$32.32	$32.30	$32.30
Purchase #3	$62.54	3.714%	$64.8627	$64.86	$64.85	$64.90
Purchase #4	$110.81	3.311%	$114.4789	$114.48	$114.50	$114.50
Purchase #5	$67.87	5.369%	$71.5139	$71.51	$71.50	$71.50
Purchase #6	$52.47	4.277%	$54.7141	$54.71	$54.70	$54.70
Purchase #7	$232.40	7.636%	$250.1461	$250.15	$250.15	$250.10
7 purchase totals =	$770.17		$810.0222	$810.01	$810.00	$810.00