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	$147.43	13.351%	$167.1134	$167.11	$167.10	$167.10
Purchase #2	$83.65	9.376%	$91.493	$91.49	$91.50	$91.50
Purchase #3	$121.64	3.671%	$126.1054	$126.11	$126.10	$126.10
Purchase #4	$205.75	9.499%	$225.2942	$225.29	$225.30	$225.30
Purchase #5	$78.39	13.348%	$88.8535	$88.85	$88.85	$88.90
Purchase #6	$22.82	11.550%	$25.4557	$25.46	$25.45	$25.50
Purchase #7	$127.53	11.445%	$142.1258	$142.13	$142.15	$142.10
7 purchase totals =	$787.21		$866.4410	$866.44	$866.45	$866.50