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	$203.71	12.529%	$229.2328	$229.23	$229.25	$229.20
Purchase #2	$12.66	6.408%	$13.4713	$13.47	$13.45	$13.50
Purchase #3	$114.86	3.526%	$118.91	$118.91	$118.90	$118.90
Purchase #4	$199.89	9.240%	$218.3598	$218.36	$218.35	$218.40
Purchase #5	$58.49	11.155%	$65.0146	$65.01	$65.00	$65.00
Purchase #6	$131.68	7.431%	$141.4651	$141.47	$141.45	$141.50
Purchase #7	$147.60	10.330%	$162.8471	$162.85	$162.85	$162.80
7 purchase totals =	$868.89		$949.3007	$949.30	$949.25	$949.30