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	$227.71	9.223%	$248.7117	$248.71	$248.70	$248.70
Purchase #2	$116.48	8.620%	$126.5206	$126.52	$126.50	$126.50
Purchase #3	$227.57	8.493%	$246.8975	$246.90	$246.90	$246.90
Purchase #4	$50.62	13.553%	$57.4805	$57.48	$57.50	$57.50
Purchase #5	$124.34	5.359%	$131.0034	$131.00	$131.00	$131.00
Purchase #6	$101.87	4.170%	$106.118	$106.12	$106.10	$106.10
Purchase #7	$189.59	3.690%	$196.5859	$196.59	$196.60	$196.60
7 purchase totals =	$1,038.18		$1,113.3176	$1,113.32	$1,113.30	$1,113.30