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	$41.89	11.524%	$46.7174	$46.72	$46.70	$46.70
Purchase #2	$59.28	11.162%	$65.8968	$65.90	$65.90	$65.90
Purchase #3	$84.61	8.123%	$91.4829	$91.48	$91.50	$91.50
Purchase #4	$79.82	3.467%	$82.5874	$82.59	$82.60	$82.60
Purchase #5	$46.54	5.584%	$49.1388	$49.14	$49.15	$49.10
Purchase #6	$104.63	9.257%	$114.3156	$114.32	$114.30	$114.30
Purchase #7	$199.57	4.403%	$208.3571	$208.36	$208.35	$208.40
7 purchase totals =	$616.34		$658.4960	$658.51	$658.50	$658.50