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	$148.90	10.195%	$164.0804	$164.08	$164.10	$164.10
Purchase #2	$219.40	9.873%	$241.0614	$241.06	$241.05	$241.10
Purchase #3	$75.75	7.314%	$81.2904	$81.29	$81.30	$81.30
Purchase #4	$226.53	13.206%	$256.4456	$256.45	$256.45	$256.40
Purchase #5	$45.94	10.726%	$50.8675	$50.87	$50.85	$50.90
Purchase #6	$51.71	7.858%	$55.7734	$55.77	$55.75	$55.80
Purchase #7	$139.35	6.224%	$148.0231	$148.02	$148.00	$148.00
7 purchase totals =	$907.58		$997.5418	$997.54	$997.50	$997.60