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	$181.57	12.705%	$204.6385	$204.64	$204.65	$204.60
Purchase #2	$161.43	10.346%	$178.1315	$178.13	$178.15	$178.10
Purchase #3	$70.43	4.389%	$73.5212	$73.52	$73.50	$73.50
Purchase #4	$195.64	12.412%	$219.9228	$219.92	$219.90	$219.90
Purchase #5	$96.52	13.160%	$109.222	$109.22	$109.20	$109.20
Purchase #6	$51.82	3.867%	$53.8239	$53.82	$53.80	$53.80
Purchase #7	$87.48	9.823%	$96.0732	$96.07	$96.05	$96.10
7 purchase totals =	$844.89		$935.3331	$935.32	$935.25	$935.20