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	$125.75	8.440%	$136.3633	$136.36	$136.35	$136.40
Purchase #2	$50.75	4.531%	$53.0495	$53.05	$53.05	$53.00
Purchase #3	$123.34	5.801%	$130.495	$130.50	$130.50	$130.50
Purchase #4	$126.38	10.616%	$139.7965	$139.80	$139.80	$139.80
Purchase #5	$170.94	6.818%	$182.5947	$182.59	$182.60	$182.60
Purchase #6	$168.78	5.822%	$178.6064	$178.61	$178.60	$178.60
Purchase #7	$59.71	11.520%	$66.5886	$66.59	$66.60	$66.60
7 purchase totals =	$825.65		$887.4940	$887.50	$887.50	$887.50