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	$76.88	7.590%	$82.7152	$82.72	$82.70	$82.70
Purchase #2	$141.51	3.554%	$146.5393	$146.54	$146.55	$146.50
Purchase #3	$7.94	6.178%	$8.4305	$8.43	$8.45	$8.40
Purchase #4	$81.78	6.480%	$87.0793	$87.08	$87.10	$87.10
Purchase #5	$96.64	6.717%	$103.1313	$103.13	$103.15	$103.10
Purchase #6	$189.94	9.562%	$208.1021	$208.10	$208.10	$208.10
Purchase #7	$166.41	3.831%	$172.7852	$172.79	$172.80	$172.80
7 purchase totals =	$761.10		$808.7829	$808.79	$808.85	$808.70