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	$5.32	4.131%	$5.5398	$5.54	$5.55	$5.50
Purchase #2	$158.66	3.452%	$164.1369	$164.14	$164.15	$164.10
Purchase #3	$167.49	4.382%	$174.8294	$174.83	$174.85	$174.80
Purchase #4	$187.27	4.640%	$195.9593	$195.96	$195.95	$196.00
Purchase #5	$33.81	5.855%	$35.7896	$35.79	$35.80	$35.80
Purchase #6	$27.31	5.165%	$28.7206	$28.72	$28.70	$28.70
Purchase #7	$59.55	8.588%	$64.6642	$64.66	$64.65	$64.70
7 purchase totals =	$639.41		$669.6398	$669.64	$669.65	$669.60