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	$164.51	3.815%	$170.7861	$170.79	$170.80	$170.80
Purchase #2	$43.39	3.864%	$45.0666	$45.07	$45.05	$45.10
Purchase #3	$44.70	3.714%	$46.3602	$46.36	$46.35	$46.40
Purchase #4	$92.33	13.229%	$104.5443	$104.54	$104.55	$104.50
Purchase #5	$230.56	5.862%	$244.0754	$244.08	$244.10	$244.10
Purchase #6	$86.56	3.613%	$89.6874	$89.69	$89.70	$89.70
Purchase #7	$169.30	10.757%	$187.5116	$187.51	$187.50	$187.50
7 purchase totals =	$831.35		$888.0316	$888.04	$888.05	$888.10