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	$48.42	12.144%	$54.3001	$54.30	$54.30	$54.30
Purchase #2	$171.59	5.401%	$180.8576	$180.86	$180.85	$180.90
Purchase #3	$125.76	12.529%	$141.5165	$141.52	$141.50	$141.50
Purchase #4	$165.59	9.632%	$181.5396	$181.54	$181.55	$181.50
Purchase #5	$176.86	11.298%	$196.8416	$196.84	$196.85	$196.80
Purchase #6	$89.83	5.522%	$94.7904	$94.79	$94.80	$94.80
Purchase #7	$138.32	4.524%	$144.5776	$144.58	$144.60	$144.60
7 purchase totals =	$916.37		$994.4234	$994.43	$994.45	$994.40