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	$135.35	11.639%	$151.1034	$151.10	$151.10	$151.10
Purchase #2	$35.36	5.398%	$37.2687	$37.27	$37.25	$37.30
Purchase #3	$148.71	13.257%	$168.4245	$168.42	$168.40	$168.40
Purchase #4	$201.53	12.700%	$227.1243	$227.12	$227.10	$227.10
Purchase #5	$110.83	5.208%	$116.602	$116.60	$116.60	$116.60
Purchase #6	$229.96	4.116%	$239.4252	$239.43	$239.45	$239.40
Purchase #7	$147.78	9.631%	$162.0127	$162.01	$162.00	$162.00
7 purchase totals =	$1,009.52		$1,101.9608	$1,101.95	$1,101.90	$1,101.90