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	$87.29	13.431%	$99.0139	$99.01	$99.00	$99.00
Purchase #2	$184.41	5.752%	$195.0173	$195.02	$195.00	$195.00
Purchase #3	$181.34	3.610%	$187.8864	$187.89	$187.90	$187.90
Purchase #4	$93.88	5.161%	$98.7251	$98.73	$98.75	$98.70
Purchase #5	$175.71	13.763%	$199.893	$199.89	$199.90	$199.90
Purchase #6	$104.86	6.298%	$111.4641	$111.46	$111.45	$111.50
Purchase #7	$247.27	3.410%	$255.7019	$255.70	$255.70	$255.70
7 purchase totals =	$1,074.76		$1,147.7017	$1,147.70	$1,147.70	$1,147.70