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	$72.49	11.860%	$81.0873	$81.09	$81.10	$81.10
Purchase #2	$31.63	12.338%	$35.5325	$35.53	$35.55	$35.50
Purchase #3	$103.88	12.511%	$116.8764	$116.88	$116.90	$116.90
Purchase #4	$161.81	5.766%	$171.14	$171.14	$171.15	$171.10
Purchase #5	$243.86	11.717%	$272.4331	$272.43	$272.45	$272.40
Purchase #6	$99.54	9.794%	$109.2889	$109.29	$109.30	$109.30
Purchase #7	$172.77	5.500%	$182.2724	$182.27	$182.25	$182.30
7 purchase totals =	$885.98		$968.6306	$968.63	$968.70	$968.60