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	$159.70	7.316%	$171.3837	$171.38	$171.40	$171.40
Purchase #2	$110.25	4.275%	$114.9632	$114.96	$114.95	$115.00
Purchase #3	$175.92	13.201%	$199.1432	$199.14	$199.15	$199.10
Purchase #4	$40.93	4.552%	$42.7931	$42.79	$42.80	$42.80
Purchase #5	$126.82	7.311%	$136.0918	$136.09	$136.10	$136.10
Purchase #6	$155.89	5.548%	$164.5388	$164.54	$164.55	$164.50
Purchase #7	$167.64	7.205%	$179.7185	$179.72	$179.70	$179.70
7 purchase totals =	$937.15		$1,008.6323	$1,008.62	$1,008.65	$1,008.60