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	$179.37	9.558%	$196.5142	$196.51	$196.50	$196.50
Purchase #2	$100.80	5.663%	$106.5083	$106.51	$106.50	$106.50
Purchase #3	$207.68	3.532%	$215.0153	$215.02	$215.00	$215.00
Purchase #4	$172.56	6.650%	$184.0352	$184.04	$184.05	$184.00
Purchase #5	$106.67	12.521%	$120.0262	$120.03	$120.05	$120.00
Purchase #6	$94.77	8.824%	$103.1325	$103.13	$103.15	$103.10
Purchase #7	$20.72	3.529%	$21.4512	$21.45	$21.45	$21.50
7 purchase totals =	$882.57		$946.6829	$946.69	$946.70	$946.60