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	$128.87	9.497%	$141.1088	$141.11	$141.10	$141.10
Purchase #2	$83.25	7.330%	$89.3522	$89.35	$89.35	$89.40
Purchase #3	$203.56	3.147%	$209.966	$209.97	$209.95	$210.00
Purchase #4	$17.31	12.405%	$19.4573	$19.46	$19.45	$19.50
Purchase #5	$132.69	11.507%	$147.9586	$147.96	$147.95	$148.00
Purchase #6	$209.55	3.732%	$217.3704	$217.37	$217.35	$217.40
Purchase #7	$125.52	4.451%	$131.1069	$131.11	$131.10	$131.10
7 purchase totals =	$900.75		$956.3202	$956.33	$956.25	$956.50