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	$214.33	13.625%	$243.5325	$243.53	$243.55	$243.50
Purchase #2	$217.42	7.586%	$233.9135	$233.91	$233.90	$233.90
Purchase #3	$173.91	5.665%	$183.762	$183.76	$183.75	$183.80
Purchase #4	$117.59	9.569%	$128.8422	$128.84	$128.85	$128.80
Purchase #5	$189.54	12.866%	$213.9262	$213.93	$213.95	$213.90
Purchase #6	$155.77	4.139%	$162.2173	$162.22	$162.20	$162.20
Purchase #7	$150.50	3.868%	$156.3213	$156.32	$156.30	$156.30
7 purchase totals =	$1,219.06		$1,322.5150	$1,322.51	$1,322.50	$1,322.40