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	$191.66	8.622%	$208.1849	$208.18	$208.20	$208.20
Purchase #2	$78.49	5.277%	$82.6319	$82.63	$82.65	$82.60
Purchase #3	$237.64	4.580%	$248.5239	$248.52	$248.50	$248.50
Purchase #4	$248.63	6.382%	$264.4976	$264.50	$264.50	$264.50
Purchase #5	$173.54	9.434%	$189.9118	$189.91	$189.90	$189.90
Purchase #6	$25.71	8.227%	$27.8252	$27.83	$27.85	$27.80
Purchase #7	$17.33	6.156%	$18.3968	$18.40	$18.40	$18.40
7 purchase totals =	$973.00		$1,039.9721	$1,039.97	$1,040.00	$1,039.90