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	$176.73	5.143%	$185.8192	$185.82	$185.80	$185.80
Purchase #2	$47.35	9.832%	$52.0055	$52.01	$52.00	$52.00
Purchase #3	$28.51	7.695%	$30.7038	$30.70	$30.70	$30.70
Purchase #4	$86.47	4.428%	$90.2989	$90.30	$90.30	$90.30
Purchase #5	$42.40	5.661%	$44.8003	$44.80	$44.80	$44.80
Purchase #6	$40.92	11.835%	$45.7629	$45.76	$45.75	$45.80
Purchase #7	$232.76	10.155%	$256.3968	$256.40	$256.40	$256.40
7 purchase totals =	$655.14		$705.7874	$705.79	$705.75	$705.80