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	$190.38	3.426%	$196.9024	$196.90	$196.90	$196.90
Purchase #2	$51.72	13.583%	$58.7451	$58.75	$58.75	$58.70
Purchase #3	$211.75	12.539%	$238.3013	$238.30	$238.30	$238.30
Purchase #4	$104.70	4.790%	$109.7151	$109.72	$109.70	$109.70
Purchase #5	$103.46	8.391%	$112.1413	$112.14	$112.15	$112.10
Purchase #6	$117.71	10.457%	$130.0189	$130.02	$130.00	$130.00
Purchase #7	$225.45	13.250%	$255.3221	$255.32	$255.30	$255.30
7 purchase totals =	$1,005.17		$1,101.1462	$1,101.15	$1,101.10	$1,101.00