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	$245.36	4.561%	$256.5509	$256.55	$256.55	$256.60
Purchase #2	$86.61	4.329%	$90.3593	$90.36	$90.35	$90.40
Purchase #3	$238.88	5.317%	$251.5812	$251.58	$251.60	$251.60
Purchase #4	$27.81	5.311%	$29.287	$29.29	$29.30	$29.30
Purchase #5	$16.96	6.804%	$18.114	$18.11	$18.10	$18.10
Purchase #6	$127.66	12.129%	$143.1439	$143.14	$143.15	$143.10
Purchase #7	$248.52	10.155%	$273.7572	$273.76	$273.75	$273.80
7 purchase totals =	$991.80		$1,062.7935	$1,062.79	$1,062.80	$1,062.90