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	$123.67	13.262%	$140.0711	$140.07	$140.05	$140.10
Purchase #2	$155.61	10.559%	$172.0409	$172.04	$172.05	$172.00
Purchase #3	$48.84	3.604%	$50.6002	$50.60	$50.60	$50.60
Purchase #4	$94.89	5.768%	$100.3633	$100.36	$100.35	$100.40
Purchase #5	$124.27	13.729%	$141.331	$141.33	$141.35	$141.30
Purchase #6	$8.27	13.184%	$9.3603	$9.36	$9.35	$9.40
Purchase #7	$67.75	12.839%	$76.4484	$76.45	$76.45	$76.40
7 purchase totals =	$623.30		$690.2152	$690.21	$690.20	$690.20