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	$59.53	5.795%	$62.9798	$62.98	$63.00	$63.00
Purchase #2	$49.85	11.279%	$55.4726	$55.47	$55.45	$55.50
Purchase #3	$92.63	7.790%	$99.8459	$99.85	$99.85	$99.80
Purchase #4	$12.59	10.787%	$13.9481	$13.95	$13.95	$13.90
Purchase #5	$127.25	8.219%	$137.7087	$137.71	$137.70	$137.70
Purchase #6	$145.29	13.154%	$164.4014	$164.40	$164.40	$164.40
Purchase #7	$30.98	5.356%	$32.6393	$32.64	$32.65	$32.60
7 purchase totals =	$518.12		$566.9958	$567.00	$567.00	$566.90