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	$105.88	10.561%	$117.062	$117.06	$117.05	$117.10
Purchase #2	$239.52	10.396%	$264.4205	$264.42	$264.40	$264.40
Purchase #3	$11.27	11.113%	$12.5224	$12.52	$12.50	$12.50
Purchase #4	$51.97	6.202%	$55.1932	$55.19	$55.20	$55.20
Purchase #5	$116.46	10.397%	$128.5683	$128.57	$128.55	$128.60
Purchase #6	$153.50	9.654%	$168.3189	$168.32	$168.30	$168.30
Purchase #7	$246.68	7.544%	$265.2895	$265.29	$265.30	$265.30
7 purchase totals =	$925.28		$1,011.3748	$1,011.37	$1,011.30	$1,011.40