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	$206.43	3.716%	$214.1009	$214.10	$214.10	$214.10
Purchase #2	$32.96	10.762%	$36.5072	$36.51	$36.50	$36.50
Purchase #3	$188.87	11.306%	$210.2236	$210.22	$210.20	$210.20
Purchase #4	$208.48	3.523%	$215.8248	$215.82	$215.80	$215.80
Purchase #5	$81.96	6.688%	$87.4415	$87.44	$87.45	$87.40
Purchase #6	$123.35	4.136%	$128.4518	$128.45	$128.45	$128.50
Purchase #7	$123.55	3.289%	$127.6136	$127.61	$127.60	$127.60
7 purchase totals =	$965.60		$1,020.1634	$1,020.15	$1,020.10	$1,020.10