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	$52.50	9.357%	$57.4124	$57.41	$57.40	$57.40
Purchase #2	$15.84	11.504%	$17.6622	$17.66	$17.65	$17.70
Purchase #3	$50.94	6.530%	$54.2664	$54.27	$54.25	$54.30
Purchase #4	$198.96	12.249%	$223.3306	$223.33	$223.35	$223.30
Purchase #5	$175.81	9.127%	$191.8562	$191.86	$191.85	$191.90
Purchase #6	$106.68	3.171%	$110.0628	$110.06	$110.05	$110.10
Purchase #7	$126.32	12.683%	$142.3412	$142.34	$142.35	$142.30
7 purchase totals =	$727.05		$796.9318	$796.93	$796.90	$797.00