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	$23.30	10.513%	$25.7495	$25.75	$25.75	$25.70
Purchase #2	$60.89	10.308%	$67.1665	$67.17	$67.15	$67.20
Purchase #3	$168.80	10.175%	$185.9754	$185.98	$186.00	$186.00
Purchase #4	$211.83	10.105%	$233.2354	$233.24	$233.25	$233.20
Purchase #5	$17.65	7.595%	$18.9905	$18.99	$19.00	$19.00
Purchase #6	$104.88	6.514%	$111.7119	$111.71	$111.70	$111.70
Purchase #7	$211.65	10.377%	$233.6129	$233.61	$233.60	$233.60
7 purchase totals =	$799.00		$876.4421	$876.45	$876.45	$876.40