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	$94.74	10.126%	$104.3334	$104.33	$104.35	$104.30
Purchase #2	$212.84	3.275%	$219.8105	$219.81	$219.80	$219.80
Purchase #3	$47.32	6.570%	$50.4289	$50.43	$50.45	$50.40
Purchase #4	$51.31	6.400%	$54.5938	$54.59	$54.60	$54.60
Purchase #5	$213.61	11.345%	$237.8441	$237.84	$237.85	$237.80
Purchase #6	$172.72	7.412%	$185.522	$185.52	$185.50	$185.50
Purchase #7	$23.65	5.382%	$24.9228	$24.92	$24.90	$24.90
7 purchase totals =	$816.19		$877.4555	$877.44	$877.45	$877.30