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	$91.78	5.102%	$96.4626	$96.46	$96.45	$96.50
Purchase #2	$104.75	4.838%	$109.8178	$109.82	$109.80	$109.80
Purchase #3	$165.39	5.479%	$174.4517	$174.45	$174.45	$174.50
Purchase #4	$92.47	11.691%	$103.2807	$103.28	$103.30	$103.30
Purchase #5	$51.55	12.442%	$57.9639	$57.96	$57.95	$58.00
Purchase #6	$236.75	10.766%	$262.2385	$262.24	$262.25	$262.20
Purchase #7	$94.40	8.694%	$102.6071	$102.61	$102.60	$102.60
7 purchase totals =	$837.09		$906.8223	$906.82	$906.80	$906.90