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	$111.75	13.856%	$127.2341	$127.23	$127.25	$127.20
Purchase #2	$86.63	11.461%	$96.5587	$96.56	$96.55	$96.60
Purchase #3	$35.85	13.127%	$40.556	$40.56	$40.55	$40.60
Purchase #4	$113.47	12.136%	$127.2407	$127.24	$127.25	$127.20
Purchase #5	$38.72	5.272%	$40.7613	$40.76	$40.75	$40.80
Purchase #6	$99.63	4.364%	$103.9779	$103.98	$104.00	$104.00
Purchase #7	$39.64	8.861%	$43.1525	$43.15	$43.15	$43.20
7 purchase totals =	$525.69		$579.4812	$579.48	$579.50	$579.60