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	$139.92	7.872%	$150.9345	$150.93	$150.95	$150.90
Purchase #2	$246.27	4.315%	$256.8966	$256.90	$256.90	$256.90
Purchase #3	$55.73	7.129%	$59.703	$59.70	$59.70	$59.70
Purchase #4	$192.64	12.571%	$216.8568	$216.86	$216.85	$216.90
Purchase #5	$210.96	13.863%	$240.2054	$240.21	$240.20	$240.20
Purchase #6	$233.50	4.131%	$243.1459	$243.15	$243.15	$243.10
Purchase #7	$52.97	12.811%	$59.756	$59.76	$59.75	$59.80
7 purchase totals =	$1,131.99		$1,227.4982	$1,227.51	$1,227.50	$1,227.50