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	$172.55	3.860%	$179.2104	$179.21	$179.20	$179.20
Purchase #2	$132.99	11.545%	$148.3437	$148.34	$148.35	$148.30
Purchase #3	$78.60	6.678%	$83.8489	$83.85	$83.85	$83.80
Purchase #4	$54.78	9.169%	$59.8028	$59.80	$59.80	$59.80
Purchase #5	$239.51	8.155%	$259.042	$259.04	$259.05	$259.00
Purchase #6	$62.32	8.300%	$67.4926	$67.49	$67.50	$67.50
Purchase #7	$142.25	3.871%	$147.7565	$147.76	$147.75	$147.80
7 purchase totals =	$883.00		$945.4969	$945.49	$945.50	$945.40