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	$139.83	8.766%	$152.0875	$152.09	$152.10	$152.10
Purchase #2	$242.92	13.365%	$275.3863	$275.39	$275.40	$275.40
Purchase #3	$47.96	9.291%	$52.416	$52.42	$52.40	$52.40
Purchase #4	$173.53	9.755%	$190.4579	$190.46	$190.45	$190.50
Purchase #5	$86.26	11.645%	$96.305	$96.31	$96.30	$96.30
Purchase #6	$196.54	12.864%	$221.8229	$221.82	$221.80	$221.80
Purchase #7	$131.71	7.290%	$141.3117	$141.31	$141.30	$141.30
7 purchase totals =	$1,018.75		$1,129.7873	$1,129.80	$1,129.75	$1,129.80