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	$243.58	5.342%	$256.592	$256.59	$256.60	$256.60
Purchase #2	$19.46	9.518%	$21.3122	$21.31	$21.30	$21.30
Purchase #3	$194.91	7.439%	$209.4094	$209.41	$209.40	$209.40
Purchase #4	$196.51	9.870%	$215.9055	$215.91	$215.90	$215.90
Purchase #5	$64.57	10.344%	$71.2491	$71.25	$71.25	$71.20
Purchase #6	$192.64	7.796%	$207.6582	$207.66	$207.65	$207.70
Purchase #7	$116.46	9.446%	$127.4608	$127.46	$127.45	$127.50
7 purchase totals =	$1,028.13		$1,109.5872	$1,109.59	$1,109.55	$1,109.60