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	$215.52	4.199%	$224.5697	$224.57	$224.55	$224.60
Purchase #2	$41.44	4.580%	$43.338	$43.34	$43.35	$43.30
Purchase #3	$82.51	3.509%	$85.4053	$85.41	$85.40	$85.40
Purchase #4	$92.86	10.709%	$102.8044	$102.80	$102.80	$102.80
Purchase #5	$62.61	5.275%	$65.9127	$65.91	$65.90	$65.90
Purchase #6	$156.56	13.822%	$178.1997	$178.20	$178.20	$178.20
Purchase #7	$115.57	7.499%	$124.2366	$124.24	$124.25	$124.20
7 purchase totals =	$767.07		$824.4664	$824.47	$824.45	$824.40