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	$201.28	12.213%	$225.8623	$225.86	$225.85	$225.90
Purchase #2	$175.48	6.628%	$187.1108	$187.11	$187.10	$187.10
Purchase #3	$53.80	10.824%	$59.6233	$59.62	$59.60	$59.60
Purchase #4	$71.91	6.838%	$76.8272	$76.83	$76.85	$76.80
Purchase #5	$19.27	3.344%	$19.9144	$19.91	$19.90	$19.90
Purchase #6	$91.71	11.346%	$102.1154	$102.12	$102.10	$102.10
Purchase #7	$205.38	4.696%	$215.0246	$215.02	$215.00	$215.00
7 purchase totals =	$818.83		$886.4780	$886.47	$886.40	$886.40