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	$148.95	13.805%	$169.5125	$169.51	$169.50	$169.50
Purchase #2	$132.53	10.218%	$146.0719	$146.07	$146.05	$146.10
Purchase #3	$66.56	7.483%	$71.5407	$71.54	$71.55	$71.50
Purchase #4	$90.46	5.432%	$95.3738	$95.37	$95.35	$95.40
Purchase #5	$39.73	7.233%	$42.6037	$42.60	$42.60	$42.60
Purchase #6	$102.73	6.415%	$109.3201	$109.32	$109.30	$109.30
Purchase #7	$226.37	5.536%	$238.9018	$238.90	$238.90	$238.90
7 purchase totals =	$807.33		$873.3245	$873.31	$873.25	$873.30