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	$124.90	3.150%	$128.8344	$128.83	$128.85	$128.80
Purchase #2	$139.40	5.159%	$146.5916	$146.59	$146.60	$146.60
Purchase #3	$6.49	12.105%	$7.2756	$7.28	$7.30	$7.30
Purchase #4	$135.78	12.102%	$152.2121	$152.21	$152.20	$152.20
Purchase #5	$250.33	5.639%	$264.4461	$264.45	$264.45	$264.40
Purchase #6	$198.57	4.469%	$207.4441	$207.44	$207.45	$207.40
Purchase #7	$127.37	10.598%	$140.8687	$140.87	$140.85	$140.90
7 purchase totals =	$982.84		$1,047.6726	$1,047.67	$1,047.70	$1,047.60