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	$178.55	6.372%	$189.9272	$189.93	$189.95	$189.90
Purchase #2	$94.98	5.835%	$100.5221	$100.52	$100.50	$100.50
Purchase #3	$229.80	12.735%	$259.065	$259.07	$259.05	$259.10
Purchase #4	$205.84	4.241%	$214.5697	$214.57	$214.55	$214.60
Purchase #5	$214.92	3.438%	$222.3089	$222.31	$222.30	$222.30
Purchase #6	$43.71	6.113%	$46.382	$46.38	$46.40	$46.40
Purchase #7	$144.61	5.212%	$152.1471	$152.15	$152.15	$152.10
7 purchase totals =	$1,112.41		$1,184.9220	$1,184.93	$1,184.90	$1,184.90