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	$40.44	13.239%	$45.7939	$45.79	$45.80	$45.80
Purchase #2	$101.61	7.771%	$109.5061	$109.51	$109.50	$109.50
Purchase #3	$63.70	13.708%	$72.432	$72.43	$72.45	$72.40
Purchase #4	$96.64	6.194%	$102.6259	$102.63	$102.65	$102.60
Purchase #5	$150.36	6.627%	$160.3244	$160.32	$160.30	$160.30
Purchase #6	$184.60	6.143%	$195.94	$195.94	$195.95	$195.90
Purchase #7	$75.52	10.325%	$83.3174	$83.32	$83.30	$83.30
7 purchase totals =	$712.87		$769.9397	$769.94	$769.95	$769.80