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	$143.48	6.255%	$152.4547	$152.45	$152.45	$152.50
Purchase #2	$25.99	9.629%	$28.4926	$28.49	$28.50	$28.50
Purchase #3	$155.41	4.538%	$162.4625	$162.46	$162.45	$162.50
Purchase #4	$247.30	3.315%	$255.498	$255.50	$255.50	$255.50
Purchase #5	$117.87	11.836%	$131.8211	$131.82	$131.80	$131.80
Purchase #6	$233.25	6.518%	$248.4532	$248.45	$248.45	$248.50
Purchase #7	$9.58	8.398%	$10.3845	$10.38	$10.40	$10.40
7 purchase totals =	$932.88		$989.5666	$989.55	$989.55	$989.70