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	$206.26	7.765%	$222.2761	$222.28	$222.30	$222.30
Purchase #2	$94.64	10.853%	$104.9113	$104.91	$104.90	$104.90
Purchase #3	$16.65	13.115%	$18.8336	$18.83	$18.85	$18.80
Purchase #4	$119.54	6.401%	$127.1918	$127.19	$127.20	$127.20
Purchase #5	$93.95	11.263%	$104.5316	$104.53	$104.55	$104.50
Purchase #6	$159.39	3.419%	$164.8395	$164.84	$164.85	$164.80
Purchase #7	$26.31	6.150%	$27.9281	$27.93	$27.95	$27.90
7 purchase totals =	$716.74		$770.5120	$770.51	$770.60	$770.40