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	$151.54	11.460%	$168.9065	$168.91	$168.90	$168.90
Purchase #2	$126.95	3.368%	$131.2257	$131.23	$131.25	$131.20
Purchase #3	$85.89	12.684%	$96.7843	$96.78	$96.80	$96.80
Purchase #4	$140.70	7.188%	$150.8135	$150.81	$150.80	$150.80
Purchase #5	$192.94	7.734%	$207.862	$207.86	$207.85	$207.90
Purchase #6	$48.85	4.487%	$51.0419	$51.04	$51.05	$51.00
Purchase #7	$210.67	5.751%	$222.7856	$222.79	$222.80	$222.80
7 purchase totals =	$957.54		$1,029.4195	$1,029.42	$1,029.45	$1,029.40