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	$247.33	9.678%	$271.2666	$271.27	$271.25	$271.30
Purchase #2	$197.78	8.203%	$214.0039	$214.00	$214.00	$214.00
Purchase #3	$35.57	12.156%	$39.8939	$39.89	$39.90	$39.90
Purchase #4	$52.41	9.726%	$57.5074	$57.51	$57.50	$57.50
Purchase #5	$138.78	7.162%	$148.7194	$148.72	$148.70	$148.70
Purchase #6	$238.46	6.661%	$254.3438	$254.34	$254.35	$254.30
Purchase #7	$73.56	6.726%	$78.5076	$78.51	$78.50	$78.50
7 purchase totals =	$983.89		$1,064.2426	$1,064.24	$1,064.20	$1,064.20