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	$94.58	7.390%	$101.5695	$101.57	$101.55	$101.60
Purchase #2	$139.38	8.592%	$151.3555	$151.36	$151.35	$151.40
Purchase #3	$78.27	5.244%	$82.3745	$82.37	$82.35	$82.40
Purchase #4	$127.71	12.487%	$143.6571	$143.66	$143.65	$143.70
Purchase #5	$244.41	8.642%	$265.5319	$265.53	$265.55	$265.50
Purchase #6	$227.26	5.106%	$238.8639	$238.86	$238.85	$238.90
Purchase #7	$213.66	6.764%	$228.112	$228.11	$228.10	$228.10
7 purchase totals =	$1,125.27		$1,211.4644	$1,211.46	$1,211.40	$1,211.60