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	$112.69	6.551%	$120.0723	$120.07	$120.05	$120.10
Purchase #2	$248.27	13.442%	$281.6425	$281.64	$281.65	$281.60
Purchase #3	$43.71	3.587%	$45.2779	$45.28	$45.30	$45.30
Purchase #4	$155.60	6.679%	$165.9925	$165.99	$166.00	$166.00
Purchase #5	$179.47	11.648%	$200.3747	$200.37	$200.35	$200.40
Purchase #6	$119.84	3.428%	$123.9481	$123.95	$123.95	$123.90
Purchase #7	$173.83	7.310%	$186.537	$186.54	$186.55	$186.50
7 purchase totals =	$1,033.41		$1,123.8450	$1,123.84	$1,123.85	$1,123.80