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	$100.57	10.777%	$111.4084	$111.41	$111.40	$111.40
Purchase #2	$154.78	8.714%	$168.2675	$168.27	$168.25	$168.30
Purchase #3	$219.91	6.645%	$234.523	$234.52	$234.50	$234.50
Purchase #4	$239.68	5.705%	$253.3537	$253.35	$253.35	$253.40
Purchase #5	$220.50	13.444%	$250.144	$250.14	$250.15	$250.10
Purchase #6	$106.35	10.270%	$117.2721	$117.27	$117.25	$117.30
Purchase #7	$40.38	5.161%	$42.464	$42.46	$42.45	$42.50
7 purchase totals =	$1,082.17		$1,177.4327	$1,177.42	$1,177.35	$1,177.50