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	$226.34	5.327%	$238.3971	$238.40	$238.40	$238.40
Purchase #2	$125.96	4.447%	$131.5614	$131.56	$131.55	$131.60
Purchase #3	$59.51	9.275%	$65.0296	$65.03	$65.05	$65.00
Purchase #4	$142.63	13.578%	$161.9963	$162.00	$162.00	$162.00
Purchase #5	$130.42	11.394%	$145.2801	$145.28	$145.30	$145.30
Purchase #6	$137.39	9.565%	$150.5314	$150.53	$150.55	$150.50
Purchase #7	$6.32	5.312%	$6.6557	$6.66	$6.65	$6.70
7 purchase totals =	$828.57		$899.4516	$899.46	$899.50	$899.50