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	$171.64	12.309%	$192.7672	$192.77	$192.75	$192.80
Purchase #2	$162.31	11.736%	$181.3587	$181.36	$181.35	$181.40
Purchase #3	$248.28	4.492%	$259.4327	$259.43	$259.45	$259.40
Purchase #4	$133.34	9.241%	$145.6619	$145.66	$145.65	$145.70
Purchase #5	$120.37	9.765%	$132.1241	$132.12	$132.10	$132.10
Purchase #6	$76.82	11.228%	$85.4453	$85.45	$85.45	$85.40
Purchase #7	$80.95	5.686%	$85.5528	$85.55	$85.55	$85.60
7 purchase totals =	$993.71		$1,082.3427	$1,082.34	$1,082.30	$1,082.40