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	$97.93	11.727%	$109.4143	$109.41	$109.40	$109.40
Purchase #2	$250.72	4.452%	$261.8821	$261.88	$261.90	$261.90
Purchase #3	$105.36	5.860%	$111.5341	$111.53	$111.55	$111.50
Purchase #4	$188.90	10.487%	$208.7099	$208.71	$208.70	$208.70
Purchase #5	$201.44	6.696%	$214.9284	$214.93	$214.95	$214.90
Purchase #6	$116.60	10.378%	$128.7007	$128.70	$128.70	$128.70
Purchase #7	$74.82	10.754%	$82.8661	$82.87	$82.85	$82.90
7 purchase totals =	$1,035.77		$1,118.0356	$1,118.03	$1,118.05	$1,118.00