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	$15.89	6.552%	$16.9311	$16.93	$16.95	$16.90
Purchase #2	$233.81	8.688%	$254.1234	$254.12	$254.10	$254.10
Purchase #3	$133.54	13.391%	$151.4223	$151.42	$151.40	$151.40
Purchase #4	$240.37	6.743%	$256.5781	$256.58	$256.60	$256.60
Purchase #5	$186.98	6.730%	$199.5638	$199.56	$199.55	$199.60
Purchase #6	$117.67	11.543%	$131.2526	$131.25	$131.25	$131.30
Purchase #7	$13.67	11.786%	$15.2811	$15.28	$15.30	$15.30
7 purchase totals =	$941.93		$1,025.1524	$1,025.14	$1,025.15	$1,025.20