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	$210.30	4.735%	$220.2577	$220.26	$220.25	$220.30
Purchase #2	$216.87	7.687%	$233.5408	$233.54	$233.55	$233.50
Purchase #3	$29.40	7.300%	$31.5462	$31.55	$31.55	$31.50
Purchase #4	$249.74	4.857%	$261.8699	$261.87	$261.85	$261.90
Purchase #5	$243.89	8.615%	$264.9011	$264.90	$264.90	$264.90
Purchase #6	$143.75	12.809%	$162.1629	$162.16	$162.15	$162.20
Purchase #7	$250.39	8.870%	$272.5996	$272.60	$272.60	$272.60
7 purchase totals =	$1,344.34		$1,446.8782	$1,446.88	$1,446.85	$1,446.90