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	$197.32	3.615%	$204.4531	$204.45	$204.45	$204.50
Purchase #2	$132.92	11.306%	$147.9479	$147.95	$147.95	$147.90
Purchase #3	$80.58	12.413%	$90.5824	$90.58	$90.60	$90.60
Purchase #4	$240.34	13.264%	$272.2187	$272.22	$272.20	$272.20
Purchase #5	$65.34	3.357%	$67.5335	$67.53	$67.55	$67.50
Purchase #6	$96.75	5.307%	$101.8845	$101.88	$101.90	$101.90
Purchase #7	$32.64	9.173%	$35.6341	$35.63	$35.65	$35.60
7 purchase totals =	$845.89		$920.2542	$920.24	$920.30	$920.20