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	$174.46	9.525%	$191.0773	$191.08	$191.10	$191.10
Purchase #2	$65.73	9.300%	$71.8429	$71.84	$71.85	$71.80
Purchase #3	$14.37	7.392%	$15.4322	$15.43	$15.45	$15.40
Purchase #4	$240.30	6.850%	$256.7606	$256.76	$256.75	$256.80
Purchase #5	$91.86	11.563%	$102.4818	$102.48	$102.50	$102.50
Purchase #6	$150.37	5.387%	$158.4704	$158.47	$158.45	$158.50
Purchase #7	$211.98	6.529%	$225.8202	$225.82	$225.80	$225.80
7 purchase totals =	$949.07		$1,021.8854	$1,021.88	$1,021.90	$1,021.90