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	$56.96	4.156%	$59.3273	$59.33	$59.35	$59.30
Purchase #2	$64.41	11.308%	$71.6935	$71.69	$71.70	$71.70
Purchase #3	$62.80	10.834%	$69.6038	$69.60	$69.60	$69.60
Purchase #4	$166.98	9.548%	$182.9233	$182.92	$182.90	$182.90
Purchase #5	$35.93	13.733%	$40.8643	$40.86	$40.85	$40.90
Purchase #6	$72.51	11.106%	$80.563	$80.56	$80.55	$80.60
Purchase #7	$106.70	4.263%	$111.2486	$111.25	$111.25	$111.20
7 purchase totals =	$566.29		$616.2238	$616.21	$616.20	$616.20