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	$168.59	6.749%	$179.9681	$179.97	$179.95	$180.00
Purchase #2	$52.49	4.546%	$54.8762	$54.88	$54.90	$54.90
Purchase #3	$35.62	13.806%	$40.5377	$40.54	$40.55	$40.50
Purchase #4	$84.67	13.664%	$96.2393	$96.24	$96.25	$96.20
Purchase #5	$190.64	10.200%	$210.0853	$210.09	$210.10	$210.10
Purchase #6	$240.87	13.569%	$273.5537	$273.55	$273.55	$273.60
Purchase #7	$243.55	11.787%	$272.2572	$272.26	$272.25	$272.30
7 purchase totals =	$1,016.43		$1,127.5175	$1,127.53	$1,127.55	$1,127.60