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	$49.48	4.225%	$51.5705	$51.57	$51.55	$51.60
Purchase #2	$28.36	6.642%	$30.2437	$30.24	$30.25	$30.20
Purchase #3	$124.83	11.769%	$139.5212	$139.52	$139.50	$139.50
Purchase #4	$228.43	8.254%	$247.2846	$247.28	$247.30	$247.30
Purchase #5	$194.30	7.146%	$208.1847	$208.18	$208.20	$208.20
Purchase #6	$224.38	4.526%	$234.5354	$234.54	$234.55	$234.50
Purchase #7	$184.95	8.334%	$200.3637	$200.36	$200.35	$200.40
7 purchase totals =	$1,034.73		$1,111.7038	$1,111.69	$1,111.70	$1,111.70