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	$82.59	11.571%	$92.1465	$92.15	$92.15	$92.10
Purchase #2	$227.41	13.177%	$257.3758	$257.38	$257.40	$257.40
Purchase #3	$95.84	5.374%	$100.9904	$100.99	$101.00	$101.00
Purchase #4	$195.93	10.809%	$217.1081	$217.11	$217.10	$217.10
Purchase #5	$98.83	13.120%	$111.7965	$111.80	$111.80	$111.80
Purchase #6	$78.87	13.141%	$89.2343	$89.23	$89.25	$89.20
Purchase #7	$141.41	10.762%	$156.6285	$156.63	$156.65	$156.60
7 purchase totals =	$920.88		$1,025.2801	$1,025.29	$1,025.35	$1,025.20