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	$153.27	9.706%	$168.1464	$168.15	$168.15	$168.10
Purchase #2	$67.66	8.810%	$73.6208	$73.62	$73.60	$73.60
Purchase #3	$176.88	11.297%	$196.8621	$196.86	$196.85	$196.90
Purchase #4	$144.64	6.514%	$154.0618	$154.06	$154.05	$154.10
Purchase #5	$139.61	9.298%	$152.5909	$152.59	$152.60	$152.60
Purchase #6	$169.39	5.370%	$178.4862	$178.49	$178.50	$178.50
Purchase #7	$55.48	11.522%	$61.8724	$61.87	$61.85	$61.90
7 purchase totals =	$906.93		$985.6406	$985.64	$985.60	$985.70