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	$98.68	6.481%	$105.0755	$105.08	$105.10	$105.10
Purchase #2	$141.73	7.820%	$152.8133	$152.81	$152.80	$152.80
Purchase #3	$85.64	6.104%	$90.8675	$90.87	$90.85	$90.90
Purchase #4	$6.57	12.450%	$7.388	$7.39	$7.40	$7.40
Purchase #5	$166.87	6.355%	$177.4746	$177.47	$177.45	$177.50
Purchase #6	$60.32	6.457%	$64.2149	$64.21	$64.20	$64.20
Purchase #7	$150.60	11.238%	$167.5244	$167.52	$167.50	$167.50
7 purchase totals =	$710.41		$765.3582	$765.35	$765.30	$765.40