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	$171.39	6.475%	$182.4875	$182.49	$182.50	$182.50
Purchase #2	$226.94	10.473%	$250.7074	$250.71	$250.70	$250.70
Purchase #3	$145.91	4.806%	$152.9224	$152.92	$152.90	$152.90
Purchase #4	$87.39	5.450%	$92.1528	$92.15	$92.15	$92.20
Purchase #5	$12.50	11.563%	$13.9454	$13.95	$13.95	$13.90
Purchase #6	$194.47	12.439%	$218.6601	$218.66	$218.65	$218.70
Purchase #7	$85.38	11.804%	$95.4583	$95.46	$95.45	$95.50
7 purchase totals =	$923.98		$1,006.3339	$1,006.34	$1,006.30	$1,006.40