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	$234.42	4.531%	$245.0416	$245.04	$245.05	$245.00
Purchase #2	$96.34	5.231%	$101.3795	$101.38	$101.40	$101.40
Purchase #3	$17.38	13.669%	$19.7557	$19.76	$19.75	$19.80
Purchase #4	$118.98	3.688%	$123.368	$123.37	$123.35	$123.40
Purchase #5	$151.75	11.426%	$169.089	$169.09	$169.10	$169.10
Purchase #6	$124.41	13.221%	$140.8582	$140.86	$140.85	$140.90
Purchase #7	$193.32	13.330%	$219.0896	$219.09	$219.10	$219.10
7 purchase totals =	$936.60		$1,018.5816	$1,018.59	$1,018.60	$1,018.70