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	$237.55	3.636%	$246.1873	$246.19	$246.20	$246.20
Purchase #2	$37.92	7.422%	$40.7344	$40.73	$40.75	$40.70
Purchase #3	$97.55	4.113%	$101.5622	$101.56	$101.55	$101.60
Purchase #4	$75.56	3.854%	$78.4721	$78.47	$78.45	$78.50
Purchase #5	$197.53	10.518%	$218.3062	$218.31	$218.30	$218.30
Purchase #6	$98.56	10.712%	$109.1177	$109.12	$109.10	$109.10
Purchase #7	$89.48	3.480%	$92.5939	$92.59	$92.60	$92.60
7 purchase totals =	$834.15		$886.9738	$886.97	$886.95	$887.00