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	$171.65	6.584%	$182.9514	$182.95	$182.95	$183.00
Purchase #2	$129.61	7.606%	$139.4681	$139.47	$139.45	$139.50
Purchase #3	$55.34	7.853%	$59.6859	$59.69	$59.70	$59.70
Purchase #4	$91.99	3.844%	$95.5261	$95.53	$95.55	$95.50
Purchase #5	$177.51	4.305%	$185.1518	$185.15	$185.15	$185.20
Purchase #6	$204.77	9.838%	$224.9153	$224.92	$224.90	$224.90
Purchase #7	$75.61	7.640%	$81.3866	$81.39	$81.40	$81.40
7 purchase totals =	$906.48		$969.0852	$969.10	$969.10	$969.20