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	$209.25	6.153%	$222.1252	$222.13	$222.15	$222.10
Purchase #2	$195.30	5.154%	$205.3658	$205.37	$205.35	$205.40
Purchase #3	$184.63	3.230%	$190.5935	$190.59	$190.60	$190.60
Purchase #4	$26.60	7.379%	$28.5628	$28.56	$28.55	$28.60
Purchase #5	$33.57	6.422%	$35.7259	$35.73	$35.75	$35.70
Purchase #6	$56.39	4.720%	$59.0516	$59.05	$59.05	$59.10
Purchase #7	$182.48	9.247%	$199.3539	$199.35	$199.35	$199.40
7 purchase totals =	$888.22		$940.7787	$940.78	$940.80	$940.90