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	$185.40	13.534%	$210.492	$210.49	$210.50	$210.50
Purchase #2	$202.86	10.650%	$224.4646	$224.46	$224.45	$224.50
Purchase #3	$173.57	6.672%	$185.1506	$185.15	$185.15	$185.20
Purchase #4	$31.88	11.372%	$35.5054	$35.51	$35.50	$35.50
Purchase #5	$140.46	12.114%	$157.4753	$157.48	$157.50	$157.50
Purchase #6	$69.30	3.850%	$71.9681	$71.97	$71.95	$72.00
Purchase #7	$229.50	8.657%	$249.3678	$249.37	$249.35	$249.40
7 purchase totals =	$1,032.97		$1,134.4238	$1,134.43	$1,134.40	$1,134.60