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	$40.29	3.654%	$41.7622	$41.76	$41.75	$41.80
Purchase #2	$74.37	4.510%	$77.7241	$77.72	$77.70	$77.70
Purchase #3	$130.49	3.589%	$135.1733	$135.17	$135.15	$135.20
Purchase #4	$233.53	9.534%	$255.7948	$255.79	$255.80	$255.80
Purchase #5	$164.71	4.846%	$172.6918	$172.69	$172.70	$172.70
Purchase #6	$156.45	7.748%	$168.5717	$168.57	$168.55	$168.60
Purchase #7	$172.46	8.610%	$187.3088	$187.31	$187.30	$187.30
7 purchase totals =	$972.30		$1,039.0267	$1,039.01	$1,038.95	$1,039.10