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	$189.86	7.669%	$204.4204	$204.42	$204.40	$204.40
Purchase #2	$128.78	10.693%	$142.5504	$142.55	$142.55	$142.60
Purchase #3	$90.33	4.455%	$94.3542	$94.35	$94.35	$94.40
Purchase #4	$85.55	11.487%	$95.3771	$95.38	$95.40	$95.40
Purchase #5	$203.79	6.742%	$217.5295	$217.53	$217.55	$217.50
Purchase #6	$176.74	13.530%	$200.6529	$200.65	$200.65	$200.70
Purchase #7	$93.29	12.582%	$105.0277	$105.03	$105.05	$105.00
7 purchase totals =	$968.34		$1,059.9122	$1,059.91	$1,059.95	$1,060.00