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	$201.65	5.574%	$212.89	$212.89	$212.90	$212.90
Purchase #2	$194.55	12.305%	$218.4894	$218.49	$218.50	$218.50
Purchase #3	$95.87	3.784%	$99.4977	$99.50	$99.50	$99.50
Purchase #4	$83.96	11.371%	$93.5071	$93.51	$93.50	$93.50
Purchase #5	$240.47	6.245%	$255.4874	$255.49	$255.50	$255.50
Purchase #6	$87.73	4.372%	$91.5656	$91.57	$91.55	$91.60
Purchase #7	$58.84	7.651%	$63.3418	$63.34	$63.35	$63.30
7 purchase totals =	$963.07		$1,034.7790	$1,034.79	$1,034.80	$1,034.80