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	$55.39	4.121%	$57.6726	$57.67	$57.65	$57.70
Purchase #2	$148.89	7.648%	$160.2771	$160.28	$160.30	$160.30
Purchase #3	$136.42	12.798%	$153.879	$153.88	$153.90	$153.90
Purchase #4	$87.58	8.629%	$95.1373	$95.14	$95.15	$95.10
Purchase #5	$83.51	6.682%	$89.0901	$89.09	$89.10	$89.10
Purchase #6	$77.82	3.809%	$80.7842	$80.78	$80.80	$80.80
Purchase #7	$197.78	10.217%	$217.9872	$217.99	$218.00	$218.00
7 purchase totals =	$787.39		$854.8275	$854.83	$854.90	$854.90