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	$172.62	7.212%	$185.0694	$185.07	$185.05	$185.10
Purchase #2	$132.26	7.279%	$141.8872	$141.89	$141.90	$141.90
Purchase #3	$230.48	6.798%	$246.148	$246.15	$246.15	$246.10
Purchase #4	$197.59	6.516%	$210.465	$210.47	$210.45	$210.50
Purchase #5	$248.34	9.659%	$272.3272	$272.33	$272.35	$272.30
Purchase #6	$186.83	3.251%	$192.9038	$192.90	$192.90	$192.90
Purchase #7	$79.57	12.491%	$89.5091	$89.51	$89.50	$89.50
7 purchase totals =	$1,247.69		$1,338.3097	$1,338.32	$1,338.30	$1,338.30