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	$55.30	7.143%	$59.2501	$59.25	$59.25	$59.30
Purchase #2	$154.69	4.319%	$161.3711	$161.37	$161.35	$161.40
Purchase #3	$189.73	12.175%	$212.8296	$212.83	$212.85	$212.80
Purchase #4	$238.81	6.842%	$255.1494	$255.15	$255.15	$255.10
Purchase #5	$133.25	4.612%	$139.3955	$139.40	$139.40	$139.40
Purchase #6	$136.93	12.336%	$153.8217	$153.82	$153.80	$153.80
Purchase #7	$62.60	4.322%	$65.3056	$65.31	$65.30	$65.30
7 purchase totals =	$971.31		$1,047.1230	$1,047.13	$1,047.10	$1,047.10