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	$141.30	12.221%	$158.5683	$158.57	$158.55	$158.60
Purchase #2	$113.69	4.240%	$118.5105	$118.51	$118.50	$118.50
Purchase #3	$20.32	9.835%	$22.3185	$22.32	$22.30	$22.30
Purchase #4	$98.26	11.399%	$109.4607	$109.46	$109.45	$109.50
Purchase #5	$225.92	6.485%	$240.5709	$240.57	$240.55	$240.60
Purchase #6	$210.41	12.627%	$236.9785	$236.98	$237.00	$237.00
Purchase #7	$160.48	7.472%	$172.4711	$172.47	$172.45	$172.50
7 purchase totals =	$970.38		$1,058.8785	$1,058.88	$1,058.80	$1,059.00