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	$111.52	5.320%	$117.4529	$117.45	$117.45	$117.50
Purchase #2	$138.78	10.205%	$152.9425	$152.94	$152.95	$152.90
Purchase #3	$12.56	6.185%	$13.3368	$13.34	$13.35	$13.30
Purchase #4	$26.97	7.576%	$29.0132	$29.01	$29.00	$29.00
Purchase #5	$137.73	13.658%	$156.5412	$156.54	$156.55	$156.50
Purchase #6	$147.71	3.479%	$152.8488	$152.85	$152.85	$152.80
Purchase #7	$228.95	11.312%	$254.8488	$254.85	$254.85	$254.80
7 purchase totals =	$804.22		$876.9842	$876.98	$877.00	$876.80