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	$80.57	10.484%	$89.017	$89.02	$89.00	$89.00
Purchase #2	$126.69	9.789%	$139.0917	$139.09	$139.10	$139.10
Purchase #3	$85.92	13.219%	$97.2778	$97.28	$97.30	$97.30
Purchase #4	$189.83	5.698%	$200.6465	$200.65	$200.65	$200.60
Purchase #5	$177.41	10.616%	$196.2438	$196.24	$196.25	$196.20
Purchase #6	$177.39	13.110%	$200.6458	$200.65	$200.65	$200.60
Purchase #7	$188.53	8.242%	$204.0686	$204.07	$204.05	$204.10
7 purchase totals =	$1,026.34		$1,126.9912	$1,127.00	$1,127.00	$1,126.90