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	$225.59	8.770%	$245.3742	$245.37	$245.35	$245.40
Purchase #2	$227.70	9.148%	$248.53	$248.53	$248.55	$248.50
Purchase #3	$89.45	10.683%	$99.0059	$99.01	$99.00	$99.00
Purchase #4	$234.89	10.687%	$259.9927	$259.99	$260.00	$260.00
Purchase #5	$76.35	8.521%	$82.8558	$82.86	$82.85	$82.90
Purchase #6	$59.30	4.759%	$62.1221	$62.12	$62.10	$62.10
Purchase #7	$40.91	9.708%	$44.8815	$44.88	$44.90	$44.90
7 purchase totals =	$954.19		$1,042.7622	$1,042.76	$1,042.75	$1,042.80