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	$73.85	8.572%	$80.1804	$80.18	$80.20	$80.20
Purchase #2	$12.87	12.802%	$14.5176	$14.52	$14.50	$14.50
Purchase #3	$42.55	7.765%	$45.854	$45.85	$45.85	$45.90
Purchase #4	$86.61	7.129%	$92.7844	$92.78	$92.80	$92.80
Purchase #5	$132.29	9.538%	$144.9078	$144.91	$144.90	$144.90
Purchase #6	$240.74	7.468%	$258.7185	$258.72	$258.70	$258.70
Purchase #7	$179.44	10.867%	$198.9397	$198.94	$198.95	$198.90
7 purchase totals =	$768.35		$835.9024	$835.90	$835.90	$835.90