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	$6.95	5.318%	$7.3196	$7.32	$7.30	$7.30
Purchase #2	$127.80	4.534%	$133.5945	$133.59	$133.60	$133.60
Purchase #3	$131.97	11.259%	$146.8285	$146.83	$146.85	$146.80
Purchase #4	$227.88	12.404%	$256.1462	$256.15	$256.15	$256.10
Purchase #5	$211.34	10.864%	$234.3	$234.30	$234.30	$234.30
Purchase #6	$64.37	9.376%	$70.4053	$70.41	$70.40	$70.40
Purchase #7	$156.38	8.534%	$169.7255	$169.73	$169.75	$169.70
7 purchase totals =	$926.69		$1,018.3196	$1,018.33	$1,018.35	$1,018.20