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	$168.67	4.488%	$176.2399	$176.24	$176.25	$176.20
Purchase #2	$231.29	13.683%	$262.9374	$262.94	$262.95	$262.90
Purchase #3	$45.59	5.148%	$47.937	$47.94	$47.95	$47.90
Purchase #4	$54.48	9.247%	$59.5178	$59.52	$59.50	$59.50
Purchase #5	$95.89	4.219%	$99.9356	$99.94	$99.95	$99.90
Purchase #6	$82.30	10.473%	$90.9193	$90.92	$90.90	$90.90
Purchase #7	$237.90	7.123%	$254.8456	$254.85	$254.85	$254.80
7 purchase totals =	$916.12		$992.3326	$992.35	$992.35	$992.10