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	$155.52	4.356%	$162.2945	$162.29	$162.30	$162.30
Purchase #2	$31.68	8.808%	$34.4704	$34.47	$34.45	$34.50
Purchase #3	$205.97	7.850%	$222.1386	$222.14	$222.15	$222.10
Purchase #4	$214.34	12.191%	$240.4702	$240.47	$240.45	$240.50
Purchase #5	$217.42	11.199%	$241.7689	$241.77	$241.75	$241.80
Purchase #6	$62.26	8.749%	$67.7071	$67.71	$67.70	$67.70
Purchase #7	$68.93	3.445%	$71.3046	$71.30	$71.30	$71.30
7 purchase totals =	$956.12		$1,040.1543	$1,040.15	$1,040.10	$1,040.20