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	$105.58	12.724%	$119.014	$119.01	$119.00	$119.00
Purchase #2	$234.39	13.272%	$265.4982	$265.50	$265.50	$265.50
Purchase #3	$233.31	7.196%	$250.099	$250.10	$250.10	$250.10
Purchase #4	$36.85	11.533%	$41.0999	$41.10	$41.10	$41.10
Purchase #5	$54.63	8.148%	$59.0813	$59.08	$59.10	$59.10
Purchase #6	$158.62	3.797%	$164.6428	$164.64	$164.65	$164.60
Purchase #7	$146.96	13.342%	$166.5674	$166.57	$166.55	$166.60
7 purchase totals =	$970.34		$1,066.0026	$1,066.00	$1,066.00	$1,066.00