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	$89.93	7.539%	$96.7098	$96.71	$96.70	$96.70
Purchase #2	$85.37	6.190%	$90.6544	$90.65	$90.65	$90.70
Purchase #3	$18.94	11.560%	$21.1295	$21.13	$21.15	$21.10
Purchase #4	$147.97	4.583%	$154.7515	$154.75	$154.75	$154.80
Purchase #5	$169.40	12.508%	$190.5886	$190.59	$190.60	$190.60
Purchase #6	$117.46	12.209%	$131.8007	$131.80	$131.80	$131.80
Purchase #7	$7.87	9.237%	$8.597	$8.60	$8.60	$8.60
7 purchase totals =	$636.94		$694.2315	$694.23	$694.25	$694.30