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	$149.67	11.174%	$166.3941	$166.39	$166.40	$166.40
Purchase #2	$170.72	5.479%	$180.0737	$180.07	$180.05	$180.10
Purchase #3	$204.64	8.750%	$222.546	$222.55	$222.55	$222.50
Purchase #4	$166.46	12.648%	$187.5139	$187.51	$187.50	$187.50
Purchase #5	$39.41	5.349%	$41.518	$41.52	$41.50	$41.50
Purchase #6	$56.78	4.438%	$59.2999	$59.30	$59.30	$59.30
Purchase #7	$135.70	10.241%	$149.597	$149.60	$149.60	$149.60
7 purchase totals =	$923.38		$1,006.9426	$1,006.94	$1,006.90	$1,006.90