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	$187.50	5.735%	$198.2531	$198.25	$198.25	$198.30
Purchase #2	$250.32	9.208%	$273.3695	$273.37	$273.35	$273.40
Purchase #3	$122.50	7.304%	$131.4474	$131.45	$131.45	$131.40
Purchase #4	$43.40	13.620%	$49.3111	$49.31	$49.30	$49.30
Purchase #5	$61.67	6.218%	$65.5046	$65.50	$65.50	$65.50
Purchase #6	$105.51	7.720%	$113.6554	$113.66	$113.65	$113.70
Purchase #7	$169.70	12.652%	$191.1704	$191.17	$191.15	$191.20
7 purchase totals =	$940.60		$1,022.7115	$1,022.71	$1,022.65	$1,022.80