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	$33.63	11.708%	$37.5674	$37.57	$37.55	$37.60
Purchase #2	$236.66	9.736%	$259.7012	$259.70	$259.70	$259.70
Purchase #3	$244.56	4.458%	$255.4625	$255.46	$255.45	$255.50
Purchase #4	$202.36	6.455%	$215.4223	$215.42	$215.40	$215.40
Purchase #5	$128.49	11.399%	$143.1366	$143.14	$143.15	$143.10
Purchase #6	$178.37	8.763%	$194.0006	$194.00	$194.00	$194.00
Purchase #7	$71.47	12.535%	$80.4288	$80.43	$80.45	$80.40
7 purchase totals =	$1,095.54		$1,185.7194	$1,185.72	$1,185.70	$1,185.70