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	$17.49	8.391%	$18.9576	$18.96	$18.95	$19.00
Purchase #2	$53.31	3.595%	$55.2265	$55.23	$55.25	$55.20
Purchase #3	$150.91	12.581%	$169.896	$169.90	$169.90	$169.90
Purchase #4	$88.57	3.696%	$91.8435	$91.84	$91.85	$91.80
Purchase #5	$26.89	7.872%	$29.0068	$29.01	$29.00	$29.00
Purchase #6	$136.54	12.682%	$153.856	$153.86	$153.85	$153.90
Purchase #7	$79.62	13.516%	$90.3814	$90.38	$90.40	$90.40
7 purchase totals =	$553.33		$609.1678	$609.18	$609.20	$609.20