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	$153.74	8.638%	$167.0201	$167.02	$167.00	$167.00
Purchase #2	$126.30	4.258%	$131.6779	$131.68	$131.70	$131.70
Purchase #3	$241.29	7.633%	$259.7077	$259.71	$259.70	$259.70
Purchase #4	$61.76	3.699%	$64.0445	$64.04	$64.05	$64.00
Purchase #5	$82.75	8.348%	$89.658	$89.66	$89.65	$89.70
Purchase #6	$164.70	4.711%	$172.459	$172.46	$172.45	$172.50
Purchase #7	$195.36	9.818%	$214.5404	$214.54	$214.55	$214.50
7 purchase totals =	$1,025.90		$1,099.1076	$1,099.11	$1,099.10	$1,099.10