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	$242.28	4.607%	$253.4418	$253.44	$253.45	$253.40
Purchase #2	$115.80	6.287%	$123.0803	$123.08	$123.10	$123.10
Purchase #3	$170.44	5.186%	$179.279	$179.28	$179.30	$179.30
Purchase #4	$56.96	10.626%	$63.0126	$63.01	$63.00	$63.00
Purchase #5	$184.36	7.511%	$198.2073	$198.21	$198.20	$198.20
Purchase #6	$81.76	12.605%	$92.0658	$92.07	$92.05	$92.10
Purchase #7	$168.90	13.514%	$191.7251	$191.73	$191.75	$191.70
7 purchase totals =	$1,020.50		$1,100.8119	$1,100.82	$1,100.85	$1,100.80