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	$223.89	13.113%	$253.2487	$253.25	$253.25	$253.20
Purchase #2	$179.75	3.118%	$185.3546	$185.35	$185.35	$185.40
Purchase #3	$95.86	9.548%	$105.0127	$105.01	$105.00	$105.00
Purchase #4	$151.35	9.581%	$165.8508	$165.85	$165.85	$165.90
Purchase #5	$201.72	3.436%	$208.6511	$208.65	$208.65	$208.70
Purchase #6	$74.73	11.316%	$83.1864	$83.19	$83.20	$83.20
Purchase #7	$71.59	4.684%	$74.9433	$74.94	$74.95	$74.90
7 purchase totals =	$998.89		$1,076.2476	$1,076.24	$1,076.25	$1,076.30