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	$63.85	4.424%	$66.6747	$66.67	$66.65	$66.70
Purchase #2	$172.54	13.615%	$196.0313	$196.03	$196.05	$196.00
Purchase #3	$144.32	10.239%	$159.0969	$159.10	$159.10	$159.10
Purchase #4	$60.38	11.817%	$67.5151	$67.52	$67.50	$67.50
Purchase #5	$220.40	10.528%	$243.6037	$243.60	$243.60	$243.60
Purchase #6	$163.33	4.457%	$170.6096	$170.61	$170.60	$170.60
Purchase #7	$66.72	4.221%	$69.5363	$69.54	$69.55	$69.50
7 purchase totals =	$891.54		$973.0676	$973.07	$973.05	$973.00