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	$67.64	6.422%	$71.9838	$71.98	$72.00	$72.00
Purchase #2	$26.29	4.756%	$27.5404	$27.54	$27.55	$27.50
Purchase #3	$167.47	6.458%	$178.2852	$178.29	$178.30	$178.30
Purchase #4	$139.39	4.298%	$145.381	$145.38	$145.40	$145.40
Purchase #5	$194.43	7.789%	$209.5742	$209.57	$209.55	$209.60
Purchase #6	$60.55	8.182%	$65.5042	$65.50	$65.50	$65.50
Purchase #7	$102.66	8.507%	$111.3933	$111.39	$111.40	$111.40
7 purchase totals =	$758.43		$809.6621	$809.65	$809.70	$809.70