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	$90.40	12.545%	$101.7407	$101.74	$101.75	$101.70
Purchase #2	$206.46	12.342%	$231.9413	$231.94	$231.95	$231.90
Purchase #3	$102.32	7.298%	$109.7873	$109.79	$109.80	$109.80
Purchase #4	$153.81	6.722%	$164.1491	$164.15	$164.15	$164.10
Purchase #5	$225.85	8.615%	$245.307	$245.31	$245.30	$245.30
Purchase #6	$16.34	7.247%	$17.5242	$17.52	$17.50	$17.50
Purchase #7	$151.32	7.656%	$162.9051	$162.91	$162.90	$162.90
7 purchase totals =	$946.50		$1,033.3547	$1,033.36	$1,033.35	$1,033.20