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	$82.42	8.135%	$89.1249	$89.12	$89.10	$89.10
Purchase #2	$83.70	8.710%	$90.9903	$90.99	$91.00	$91.00
Purchase #3	$65.51	11.165%	$72.8242	$72.82	$72.80	$72.80
Purchase #4	$72.99	4.463%	$76.2475	$76.25	$76.25	$76.20
Purchase #5	$17.99	5.703%	$19.016	$19.02	$19.00	$19.00
Purchase #6	$154.29	5.441%	$162.6849	$162.68	$162.70	$162.70
Purchase #7	$38.69	11.534%	$43.1525	$43.15	$43.15	$43.20
7 purchase totals =	$515.59		$554.0403	$554.03	$554.00	$554.00