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	$196.88	9.575%	$215.7313	$215.73	$215.75	$215.70
Purchase #2	$151.91	9.205%	$165.8933	$165.89	$165.90	$165.90
Purchase #3	$104.62	6.465%	$111.3837	$111.38	$111.40	$111.40
Purchase #4	$163.84	10.264%	$180.6565	$180.66	$180.65	$180.70
Purchase #5	$201.34	10.734%	$222.9518	$222.95	$222.95	$223.00
Purchase #6	$164.75	5.394%	$173.6366	$173.64	$173.65	$173.60
Purchase #7	$209.38	3.205%	$216.0906	$216.09	$216.10	$216.10
7 purchase totals =	$1,192.72		$1,286.3438	$1,286.34	$1,286.40	$1,286.40