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	$109.51	4.559%	$114.5026	$114.50	$114.50	$114.50
Purchase #2	$5.27	11.132%	$5.8567	$5.86	$5.85	$5.90
Purchase #3	$127.80	12.266%	$143.4759	$143.48	$143.50	$143.50
Purchase #4	$56.60	9.819%	$62.1576	$62.16	$62.15	$62.20
Purchase #5	$236.98	7.126%	$253.8672	$253.87	$253.85	$253.90
Purchase #6	$46.98	12.612%	$52.9051	$52.91	$52.90	$52.90
Purchase #7	$50.91	3.153%	$52.5152	$52.52	$52.50	$52.50
7 purchase totals =	$634.05		$685.2803	$685.30	$685.25	$685.40