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	$200.45	11.556%	$223.614	$223.61	$223.60	$223.60
Purchase #2	$29.65	4.551%	$30.9994	$31.00	$31.00	$31.00
Purchase #3	$34.55	9.740%	$37.9152	$37.92	$37.90	$37.90
Purchase #4	$195.94	7.147%	$209.9438	$209.94	$209.95	$209.90
Purchase #5	$64.61	10.606%	$71.4625	$71.46	$71.45	$71.50
Purchase #6	$190.60	10.155%	$209.9554	$209.96	$209.95	$210.00
Purchase #7	$145.56	9.603%	$159.5381	$159.54	$159.55	$159.50
7 purchase totals =	$861.36		$943.4284	$943.43	$943.40	$943.40