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	$234.99	12.775%	$265.01	$265.01	$265.00	$265.00
Purchase #2	$113.65	5.832%	$120.2781	$120.28	$120.30	$120.30
Purchase #3	$151.62	13.650%	$172.3161	$172.32	$172.30	$172.30
Purchase #4	$130.80	9.334%	$143.0089	$143.01	$143.00	$143.00
Purchase #5	$52.50	12.453%	$59.0378	$59.04	$59.05	$59.00
Purchase #6	$155.52	12.537%	$175.0175	$175.02	$175.00	$175.00
Purchase #7	$183.38	3.108%	$189.0795	$189.08	$189.10	$189.10
7 purchase totals =	$1,022.46		$1,123.7479	$1,123.76	$1,123.75	$1,123.70