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	$78.74	4.582%	$82.3479	$82.35	$82.35	$82.30
Purchase #2	$161.34	12.655%	$181.7576	$181.76	$181.75	$181.80
Purchase #3	$99.74	12.144%	$111.8524	$111.85	$111.85	$111.90
Purchase #4	$76.27	12.744%	$85.9898	$85.99	$86.00	$86.00
Purchase #5	$183.68	12.745%	$207.09	$207.09	$207.10	$207.10
Purchase #6	$188.78	5.107%	$198.421	$198.42	$198.40	$198.40
Purchase #7	$150.37	9.377%	$164.4702	$164.47	$164.45	$164.50
7 purchase totals =	$938.92		$1,031.9289	$1,031.93	$1,031.90	$1,032.00