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	$147.64	11.166%	$164.1255	$164.13	$164.15	$164.10
Purchase #2	$159.64	7.311%	$171.3113	$171.31	$171.30	$171.30
Purchase #3	$226.87	5.397%	$239.1142	$239.11	$239.10	$239.10
Purchase #4	$11.45	3.812%	$11.8865	$11.89	$11.90	$11.90
Purchase #5	$59.89	7.284%	$64.2524	$64.25	$64.25	$64.30
Purchase #6	$28.49	9.785%	$31.2777	$31.28	$31.30	$31.30
Purchase #7	$111.69	10.457%	$123.3694	$123.37	$123.35	$123.40
7 purchase totals =	$745.67		$805.3370	$805.34	$805.35	$805.40