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	$43.57	4.599%	$45.5738	$45.57	$45.55	$45.60
Purchase #2	$90.49	10.376%	$99.8792	$99.88	$99.90	$99.90
Purchase #3	$205.54	5.743%	$217.3442	$217.34	$217.35	$217.30
Purchase #4	$144.89	12.347%	$162.7796	$162.78	$162.80	$162.80
Purchase #5	$198.91	6.668%	$212.1733	$212.17	$212.15	$212.20
Purchase #6	$65.25	6.334%	$69.3829	$69.38	$69.40	$69.40
Purchase #7	$100.78	8.442%	$109.2878	$109.29	$109.30	$109.30
7 purchase totals =	$849.43		$916.4208	$916.41	$916.45	$916.50