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	$129.72	5.140%	$136.3876	$136.39	$136.40	$136.40
Purchase #2	$126.31	13.610%	$143.5008	$143.50	$143.50	$143.50
Purchase #3	$45.67	3.636%	$47.3306	$47.33	$47.35	$47.30
Purchase #4	$120.55	12.836%	$136.0238	$136.02	$136.00	$136.00
Purchase #5	$50.54	13.818%	$57.5236	$57.52	$57.50	$57.50
Purchase #6	$71.52	9.537%	$78.3409	$78.34	$78.35	$78.30
Purchase #7	$119.29	13.735%	$135.6745	$135.67	$135.65	$135.70
7 purchase totals =	$663.60		$734.7818	$734.77	$734.75	$734.70