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	$169.64	6.157%	$180.0847	$180.08	$180.10	$180.10
Purchase #2	$167.87	3.702%	$174.0845	$174.08	$174.10	$174.10
Purchase #3	$64.99	11.529%	$72.4827	$72.48	$72.50	$72.50
Purchase #4	$82.35	8.554%	$89.3942	$89.39	$89.40	$89.40
Purchase #5	$39.97	7.254%	$42.8694	$42.87	$42.85	$42.90
Purchase #6	$193.76	9.449%	$212.0684	$212.07	$212.05	$212.10
Purchase #7	$246.27	10.454%	$272.0151	$272.02	$272.00	$272.00
7 purchase totals =	$964.85		$1,042.9990	$1,042.99	$1,043.00	$1,043.10