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	$53.67	4.555%	$56.1147	$56.11	$56.10	$56.10
Purchase #2	$131.36	4.466%	$137.2265	$137.23	$137.25	$137.20
Purchase #3	$137.45	7.841%	$148.2275	$148.23	$148.25	$148.20
Purchase #4	$179.80	7.349%	$193.0135	$193.01	$193.00	$193.00
Purchase #5	$56.63	10.443%	$62.5439	$62.54	$62.55	$62.50
Purchase #6	$177.61	12.546%	$199.893	$199.89	$199.90	$199.90
Purchase #7	$88.87	10.796%	$98.4644	$98.46	$98.45	$98.50
7 purchase totals =	$825.39		$895.4835	$895.47	$895.50	$895.40