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	$36.63	11.786%	$40.9472	$40.95	$40.95	$40.90
Purchase #2	$204.90	6.608%	$218.4398	$218.44	$218.45	$218.40
Purchase #3	$35.97	4.518%	$37.5951	$37.60	$37.60	$37.60
Purchase #4	$168.81	13.748%	$192.018	$192.02	$192.00	$192.00
Purchase #5	$90.64	6.760%	$96.7673	$96.77	$96.75	$96.80
Purchase #6	$229.54	6.660%	$244.8274	$244.83	$244.85	$244.80
Purchase #7	$168.47	7.110%	$180.4482	$180.45	$180.45	$180.40
7 purchase totals =	$934.96		$1,011.0430	$1,011.06	$1,011.05	$1,010.90