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	$167.39	3.642%	$173.4863	$173.49	$173.50	$173.50
Purchase #2	$142.30	5.300%	$149.8419	$149.84	$149.85	$149.80
Purchase #3	$51.58	4.434%	$53.8671	$53.87	$53.85	$53.90
Purchase #4	$36.88	11.128%	$40.984	$40.98	$41.00	$41.00
Purchase #5	$210.37	6.504%	$224.0525	$224.05	$224.05	$224.10
Purchase #6	$97.39	8.364%	$105.5357	$105.54	$105.55	$105.50
Purchase #7	$185.69	4.724%	$194.462	$194.46	$194.45	$194.50
7 purchase totals =	$891.60		$942.2295	$942.23	$942.25	$942.30