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	$87.31	4.140%	$90.9246	$90.92	$90.90	$90.90
Purchase #2	$190.42	10.579%	$210.5645	$210.56	$210.55	$210.60
Purchase #3	$43.59	13.120%	$49.309	$49.31	$49.30	$49.30
Purchase #4	$240.51	13.743%	$273.5633	$273.56	$273.55	$273.60
Purchase #5	$169.89	13.540%	$192.8931	$192.89	$192.90	$192.90
Purchase #6	$86.70	4.440%	$90.5495	$90.55	$90.55	$90.50
Purchase #7	$221.91	7.572%	$238.713	$238.71	$238.70	$238.70
7 purchase totals =	$1,040.33		$1,146.5170	$1,146.50	$1,146.45	$1,146.50