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	$156.30	5.467%	$164.8449	$164.84	$164.85	$164.80
Purchase #2	$108.76	13.221%	$123.1392	$123.14	$123.15	$123.10
Purchase #3	$210.28	6.582%	$224.1206	$224.12	$224.10	$224.10
Purchase #4	$151.83	6.589%	$161.8341	$161.83	$161.85	$161.80
Purchase #5	$139.76	12.354%	$157.026	$157.03	$157.05	$157.00
Purchase #6	$246.93	3.829%	$256.3849	$256.38	$256.40	$256.40
Purchase #7	$187.57	4.637%	$196.2676	$196.27	$196.25	$196.30
7 purchase totals =	$1,201.43		$1,283.6173	$1,283.61	$1,283.65	$1,283.50