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	$248.89	6.778%	$265.7598	$265.76	$265.75	$265.80
Purchase #2	$243.47	4.253%	$253.8248	$253.82	$253.80	$253.80
Purchase #3	$15.32	4.121%	$15.9513	$15.95	$15.95	$16.00
Purchase #4	$190.36	13.227%	$215.5389	$215.54	$215.55	$215.50
Purchase #5	$215.42	6.724%	$229.9048	$229.90	$229.90	$229.90
Purchase #6	$77.93	7.214%	$83.5519	$83.55	$83.55	$83.60
Purchase #7	$42.52	10.633%	$47.0412	$47.04	$47.05	$47.00
7 purchase totals =	$1,033.91		$1,111.5727	$1,111.56	$1,111.55	$1,111.60