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	$168.27	6.580%	$179.3422	$179.34	$179.35	$179.30
Purchase #2	$82.90	9.397%	$90.6901	$90.69	$90.70	$90.70
Purchase #3	$140.59	10.765%	$155.7245	$155.72	$155.70	$155.70
Purchase #4	$60.60	11.614%	$67.6381	$67.64	$67.65	$67.60
Purchase #5	$141.81	6.221%	$150.632	$150.63	$150.65	$150.60
Purchase #6	$132.95	4.139%	$138.4528	$138.45	$138.45	$138.50
Purchase #7	$233.74	11.528%	$260.6855	$260.69	$260.70	$260.70
7 purchase totals =	$960.86		$1,043.1652	$1,043.16	$1,043.20	$1,043.10