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	$171.57	8.297%	$185.8052	$185.81	$185.80	$185.80
Purchase #2	$238.27	6.155%	$252.9355	$252.94	$252.95	$252.90
Purchase #3	$224.38	6.649%	$239.299	$239.30	$239.30	$239.30
Purchase #4	$55.84	12.629%	$62.892	$62.89	$62.90	$62.90
Purchase #5	$71.25	10.310%	$78.5959	$78.60	$78.60	$78.60
Purchase #6	$34.55	12.429%	$38.8442	$38.84	$38.85	$38.80
Purchase #7	$159.44	3.360%	$164.7972	$164.80	$164.80	$164.80
7 purchase totals =	$955.30		$1,023.1690	$1,023.18	$1,023.20	$1,023.10