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	$60.79	10.784%	$67.3456	$67.35	$67.35	$67.30
Purchase #2	$218.55	7.254%	$234.4036	$234.40	$234.40	$234.40
Purchase #3	$33.83	3.133%	$34.8899	$34.89	$34.90	$34.90
Purchase #4	$200.54	10.285%	$221.1655	$221.17	$221.15	$221.20
Purchase #5	$131.49	10.638%	$145.4779	$145.48	$145.50	$145.50
Purchase #6	$80.66	12.365%	$90.6336	$90.63	$90.65	$90.60
Purchase #7	$58.83	7.770%	$63.4011	$63.40	$63.40	$63.40
7 purchase totals =	$784.69		$857.3172	$857.32	$857.35	$857.30