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	$92.55	3.758%	$96.028	$96.03	$96.05	$96.00
Purchase #2	$180.62	8.778%	$196.4748	$196.47	$196.45	$196.50
Purchase #3	$250.92	13.798%	$285.5419	$285.54	$285.55	$285.50
Purchase #4	$119.46	7.621%	$128.564	$128.56	$128.55	$128.60
Purchase #5	$172.29	7.162%	$184.6294	$184.63	$184.65	$184.60
Purchase #6	$112.46	10.588%	$124.3673	$124.37	$124.35	$124.40
Purchase #7	$214.43	12.611%	$241.4718	$241.47	$241.45	$241.50
7 purchase totals =	$1,142.73		$1,257.0772	$1,257.07	$1,257.05	$1,257.10