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	$156.78	8.245%	$169.7065	$169.71	$169.70	$169.70
Purchase #2	$6.72	12.192%	$7.5393	$7.54	$7.55	$7.50
Purchase #3	$45.82	12.289%	$51.4508	$51.45	$51.45	$51.50
Purchase #4	$249.63	11.380%	$278.0379	$278.04	$278.05	$278.00
Purchase #5	$155.74	7.452%	$167.3457	$167.35	$167.35	$167.30
Purchase #6	$133.38	8.316%	$144.4719	$144.47	$144.45	$144.50
Purchase #7	$185.50	4.342%	$193.5544	$193.55	$193.55	$193.60
7 purchase totals =	$933.57		$1,012.1065	$1,012.11	$1,012.10	$1,012.10