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	$228.45	7.812%	$246.2965	$246.30	$246.30	$246.30
Purchase #2	$151.46	8.550%	$164.4098	$164.41	$164.40	$164.40
Purchase #3	$69.51	12.434%	$78.1529	$78.15	$78.15	$78.20
Purchase #4	$196.75	10.821%	$218.0403	$218.04	$218.05	$218.00
Purchase #5	$88.25	7.329%	$94.7178	$94.72	$94.70	$94.70
Purchase #6	$97.42	10.748%	$107.8907	$107.89	$107.90	$107.90
Purchase #7	$133.51	4.724%	$139.817	$139.82	$139.80	$139.80
7 purchase totals =	$965.35		$1,049.3250	$1,049.33	$1,049.30	$1,049.30