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	$99.57	11.621%	$111.141	$111.14	$111.15	$111.10
Purchase #2	$134.82	5.166%	$141.7848	$141.78	$141.80	$141.80
Purchase #3	$201.34	3.430%	$208.246	$208.25	$208.25	$208.20
Purchase #4	$175.66	11.848%	$196.4722	$196.47	$196.45	$196.50
Purchase #5	$109.64	7.594%	$117.9661	$117.97	$117.95	$118.00
Purchase #6	$64.78	12.148%	$72.6495	$72.65	$72.65	$72.60
Purchase #7	$101.49	6.804%	$108.3954	$108.40	$108.40	$108.40
7 purchase totals =	$887.30		$956.6550	$956.66	$956.65	$956.60