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	$164.38	3.363%	$169.9081	$169.91	$169.90	$169.90
Purchase #2	$53.99	9.760%	$59.2594	$59.26	$59.25	$59.30
Purchase #3	$132.35	4.690%	$138.5572	$138.56	$138.55	$138.60
Purchase #4	$52.74	6.262%	$56.0426	$56.04	$56.05	$56.00
Purchase #5	$82.48	4.621%	$86.2914	$86.29	$86.30	$86.30
Purchase #6	$134.83	6.156%	$143.1301	$143.13	$143.15	$143.10
Purchase #7	$43.56	9.645%	$47.7614	$47.76	$47.75	$47.80
7 purchase totals =	$664.33		$700.9502	$700.95	$700.95	$701.00