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	$50.96	6.802%	$54.4263	$54.43	$54.45	$54.40
Purchase #2	$100.69	12.534%	$113.3105	$113.31	$113.30	$113.30
Purchase #3	$173.80	12.779%	$196.0099	$196.01	$196.00	$196.00
Purchase #4	$110.29	9.506%	$120.7742	$120.77	$120.75	$120.80
Purchase #5	$160.84	4.142%	$167.502	$167.50	$167.50	$167.50
Purchase #6	$137.59	13.342%	$155.9473	$155.95	$155.95	$155.90
Purchase #7	$205.76	10.185%	$226.7167	$226.72	$226.70	$226.70
7 purchase totals =	$939.93		$1,034.6869	$1,034.69	$1,034.65	$1,034.60