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	$179.67	11.385%	$200.1254	$200.13	$200.15	$200.10
Purchase #2	$42.68	6.435%	$45.4265	$45.43	$45.45	$45.40
Purchase #3	$187.88	10.457%	$207.5266	$207.53	$207.55	$207.50
Purchase #4	$148.74	5.274%	$156.5845	$156.58	$156.60	$156.60
Purchase #5	$216.91	12.211%	$243.3969	$243.40	$243.40	$243.40
Purchase #6	$46.43	5.759%	$49.1039	$49.10	$49.10	$49.10
Purchase #7	$64.40	10.637%	$71.2502	$71.25	$71.25	$71.30
7 purchase totals =	$886.71		$973.4140	$973.42	$973.50	$973.40