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	$105.53	3.855%	$109.5982	$109.60	$109.60	$109.60
Purchase #2	$75.88	13.109%	$85.8271	$85.83	$85.85	$85.80
Purchase #3	$100.75	3.607%	$104.3841	$104.38	$104.40	$104.40
Purchase #4	$60.50	6.673%	$64.5372	$64.54	$64.55	$64.50
Purchase #5	$234.70	4.144%	$244.426	$244.43	$244.45	$244.40
Purchase #6	$21.78	7.212%	$23.3508	$23.35	$23.35	$23.40
Purchase #7	$97.25	5.405%	$102.5064	$102.51	$102.50	$102.50
7 purchase totals =	$696.39		$734.6298	$734.64	$734.70	$734.60