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	$124.80	5.869%	$132.1245	$132.12	$132.10	$132.10
Purchase #2	$95.53	7.359%	$102.5601	$102.56	$102.55	$102.60
Purchase #3	$81.83	10.312%	$90.2683	$90.27	$90.25	$90.30
Purchase #4	$29.36	10.329%	$32.3926	$32.39	$32.40	$32.40
Purchase #5	$28.62	12.798%	$32.2828	$32.28	$32.30	$32.30
Purchase #6	$71.25	5.496%	$75.1659	$75.17	$75.15	$75.20
Purchase #7	$213.30	3.389%	$220.5287	$220.53	$220.55	$220.50
7 purchase totals =	$644.69		$685.3229	$685.32	$685.30	$685.40