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	$195.61	6.345%	$208.0215	$208.02	$208.00	$208.00
Purchase #2	$117.80	7.217%	$126.3016	$126.30	$126.30	$126.30
Purchase #3	$121.50	4.716%	$127.2299	$127.23	$127.25	$127.20
Purchase #4	$85.49	12.669%	$96.3207	$96.32	$96.30	$96.30
Purchase #5	$89.52	13.488%	$101.5945	$101.59	$101.60	$101.60
Purchase #6	$152.88	8.839%	$166.3931	$166.39	$166.40	$166.40
Purchase #7	$227.63	6.199%	$241.7408	$241.74	$241.75	$241.70
7 purchase totals =	$990.43		$1,067.6021	$1,067.59	$1,067.60	$1,067.50