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	$179.73	10.600%	$198.7814	$198.78	$198.80	$198.80
Purchase #2	$219.25	11.664%	$244.8233	$244.82	$244.80	$244.80
Purchase #3	$176.43	4.358%	$184.1188	$184.12	$184.10	$184.10
Purchase #4	$190.37	8.394%	$206.3497	$206.35	$206.35	$206.30
Purchase #5	$63.90	13.486%	$72.5176	$72.52	$72.50	$72.50
Purchase #6	$33.95	11.281%	$37.7799	$37.78	$37.80	$37.80
Purchase #7	$96.73	4.622%	$101.2009	$101.20	$101.20	$101.20
7 purchase totals =	$960.36		$1,045.5716	$1,045.57	$1,045.55	$1,045.50