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	$154.71	12.579%	$174.171	$174.17	$174.15	$174.20
Purchase #2	$28.93	7.823%	$31.1932	$31.19	$31.20	$31.20
Purchase #3	$132.99	13.534%	$150.9889	$150.99	$151.00	$151.00
Purchase #4	$96.46	3.248%	$99.593	$99.59	$99.60	$99.60
Purchase #5	$70.58	11.232%	$78.5075	$78.51	$78.50	$78.50
Purchase #6	$212.83	3.545%	$220.3748	$220.37	$220.35	$220.40
Purchase #7	$210.88	5.273%	$221.9997	$222.00	$222.00	$222.00
7 purchase totals =	$907.38		$976.8281	$976.82	$976.80	$976.90