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	$234.83	3.804%	$243.7629	$243.76	$243.75	$243.80
Purchase #2	$80.93	5.371%	$85.2768	$85.28	$85.30	$85.30
Purchase #3	$86.36	12.816%	$97.4279	$97.43	$97.45	$97.40
Purchase #4	$7.47	11.725%	$8.3459	$8.35	$8.35	$8.30
Purchase #5	$40.31	13.720%	$45.8405	$45.84	$45.85	$45.80
Purchase #6	$175.87	8.330%	$190.52	$190.52	$190.50	$190.50
Purchase #7	$9.79	13.529%	$11.1145	$11.11	$11.10	$11.10
7 purchase totals =	$635.56		$682.2885	$682.29	$682.30	$682.20