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	$207.60	7.462%	$223.0911	$223.09	$223.10	$223.10
Purchase #2	$249.33	3.673%	$258.4879	$258.49	$258.50	$258.50
Purchase #3	$28.51	4.789%	$29.8753	$29.88	$29.90	$29.90
Purchase #4	$234.49	3.173%	$241.9304	$241.93	$241.95	$241.90
Purchase #5	$138.78	10.866%	$153.8598	$153.86	$153.85	$153.90
Purchase #6	$25.87	5.550%	$27.3058	$27.31	$27.30	$27.30
Purchase #7	$12.96	10.298%	$14.2946	$14.29	$14.30	$14.30
7 purchase totals =	$897.54		$948.8449	$948.85	$948.90	$948.90