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	$42.61	11.827%	$47.6495	$47.65	$47.65	$47.60
Purchase #2	$183.30	9.482%	$200.6805	$200.68	$200.70	$200.70
Purchase #3	$23.32	9.385%	$25.5086	$25.51	$25.50	$25.50
Purchase #4	$92.37	13.162%	$104.5277	$104.53	$104.55	$104.50
Purchase #5	$101.30	12.607%	$114.0709	$114.07	$114.05	$114.10
Purchase #6	$172.73	13.698%	$196.3906	$196.39	$196.40	$196.40
Purchase #7	$47.92	6.417%	$50.995	$51.00	$51.00	$51.00
7 purchase totals =	$663.55		$739.8228	$739.83	$739.85	$739.80