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	$150.54	12.732%	$169.7068	$169.71	$169.70	$169.70
Purchase #2	$177.92	10.348%	$196.3312	$196.33	$196.35	$196.30
Purchase #3	$154.45	4.494%	$161.391	$161.39	$161.40	$161.40
Purchase #4	$234.49	4.702%	$245.5157	$245.52	$245.50	$245.50
Purchase #5	$228.64	4.641%	$239.2512	$239.25	$239.25	$239.30
Purchase #6	$238.29	4.561%	$249.1584	$249.16	$249.15	$249.20
Purchase #7	$226.47	12.838%	$255.5442	$255.54	$255.55	$255.50
7 purchase totals =	$1,410.80		$1,516.8985	$1,516.90	$1,516.90	$1,516.90