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	$113.45	10.791%	$125.6924	$125.69	$125.70	$125.70
Purchase #2	$124.64	13.191%	$141.0813	$141.08	$141.10	$141.10
Purchase #3	$55.33	7.558%	$59.5118	$59.51	$59.50	$59.50
Purchase #4	$50.62	10.225%	$55.7959	$55.80	$55.80	$55.80
Purchase #5	$109.54	3.541%	$113.4188	$113.42	$113.40	$113.40
Purchase #6	$171.41	6.664%	$182.8328	$182.83	$182.85	$182.80
Purchase #7	$104.30	4.731%	$109.2344	$109.23	$109.25	$109.20
7 purchase totals =	$729.29		$787.5674	$787.56	$787.60	$787.50