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	$86.38	12.864%	$97.4919	$97.49	$97.50	$97.50
Purchase #2	$120.69	5.735%	$127.6116	$127.61	$127.60	$127.60
Purchase #3	$211.30	11.643%	$235.9017	$235.90	$235.90	$235.90
Purchase #4	$209.25	10.352%	$230.9116	$230.91	$230.90	$230.90
Purchase #5	$162.29	5.731%	$171.5908	$171.59	$171.60	$171.60
Purchase #6	$222.34	8.811%	$241.9304	$241.93	$241.95	$241.90
Purchase #7	$238.27	6.185%	$253.007	$253.01	$253.00	$253.00
7 purchase totals =	$1,250.52		$1,358.4450	$1,358.44	$1,358.45	$1,358.40