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	$148.40	5.743%	$156.9226	$156.92	$156.90	$156.90
Purchase #2	$179.43	5.660%	$189.5857	$189.59	$189.60	$189.60
Purchase #3	$221.59	3.172%	$228.6188	$228.62	$228.60	$228.60
Purchase #4	$71.96	4.412%	$75.1349	$75.13	$75.15	$75.10
Purchase #5	$138.93	11.825%	$155.3585	$155.36	$155.35	$155.40
Purchase #6	$77.64	3.693%	$80.5072	$80.51	$80.50	$80.50
Purchase #7	$165.83	9.770%	$182.0316	$182.03	$182.05	$182.00
7 purchase totals =	$1,003.78		$1,068.1593	$1,068.16	$1,068.15	$1,068.10