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	$120.34	9.237%	$131.4558	$131.46	$131.45	$131.50
Purchase #2	$91.31	5.241%	$96.0956	$96.10	$96.10	$96.10
Purchase #3	$230.80	13.520%	$262.0042	$262.00	$262.00	$262.00
Purchase #4	$236.86	6.753%	$252.8552	$252.86	$252.85	$252.90
Purchase #5	$89.35	3.378%	$92.3682	$92.37	$92.35	$92.40
Purchase #6	$141.66	6.484%	$150.8452	$150.85	$150.85	$150.80
Purchase #7	$150.46	3.452%	$155.6539	$155.65	$155.65	$155.70
7 purchase totals =	$1,060.78		$1,141.2781	$1,141.29	$1,141.25	$1,141.40