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	$161.96	3.571%	$167.7436	$167.74	$167.75	$167.70
Purchase #2	$36.96	12.124%	$41.441	$41.44	$41.45	$41.40
Purchase #3	$86.50	4.573%	$90.4556	$90.46	$90.45	$90.50
Purchase #4	$157.48	11.492%	$175.5776	$175.58	$175.60	$175.60
Purchase #5	$7.65	9.493%	$8.3762	$8.38	$8.40	$8.40
Purchase #6	$152.72	10.136%	$168.1997	$168.20	$168.20	$168.20
Purchase #7	$39.57	5.365%	$41.6929	$41.69	$41.70	$41.70
7 purchase totals =	$642.84		$693.4866	$693.49	$693.55	$693.50