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	$81.77	8.154%	$88.4375	$88.44	$88.45	$88.40
Purchase #2	$13.96	3.807%	$14.4915	$14.49	$14.50	$14.50
Purchase #3	$227.60	13.668%	$258.7084	$258.71	$258.70	$258.70
Purchase #4	$211.31	6.488%	$225.0198	$225.02	$225.00	$225.00
Purchase #5	$215.98	11.359%	$240.5132	$240.51	$240.50	$240.50
Purchase #6	$76.36	8.485%	$82.8391	$82.84	$82.85	$82.80
Purchase #7	$47.34	12.520%	$53.267	$53.27	$53.25	$53.30
7 purchase totals =	$874.32		$963.2765	$963.28	$963.25	$963.20