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	$226.96	9.268%	$247.9947	$247.99	$248.00	$248.00
Purchase #2	$19.62	5.443%	$20.6879	$20.69	$20.70	$20.70
Purchase #3	$170.46	11.505%	$190.0714	$190.07	$190.05	$190.10
Purchase #4	$134.34	10.786%	$148.8299	$148.83	$148.85	$148.80
Purchase #5	$119.31	4.285%	$124.4224	$124.42	$124.40	$124.40
Purchase #6	$100.27	7.601%	$107.8915	$107.89	$107.90	$107.90
Purchase #7	$233.57	13.669%	$265.4967	$265.50	$265.50	$265.50
7 purchase totals =	$1,004.53		$1,105.3945	$1,105.39	$1,105.40	$1,105.40