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	$114.88	3.874%	$119.3305	$119.33	$119.35	$119.30
Purchase #2	$128.77	8.478%	$139.6871	$139.69	$139.70	$139.70
Purchase #3	$96.35	13.620%	$109.4729	$109.47	$109.45	$109.50
Purchase #4	$212.39	8.496%	$230.4347	$230.43	$230.45	$230.40
Purchase #5	$111.25	5.129%	$116.956	$116.96	$116.95	$117.00
Purchase #6	$190.63	3.268%	$196.8598	$196.86	$196.85	$196.90
Purchase #7	$228.43	9.356%	$249.8019	$249.80	$249.80	$249.80
7 purchase totals =	$1,082.70		$1,162.5429	$1,162.54	$1,162.55	$1,162.60