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	$38.74	11.110%	$43.044	$43.04	$43.05	$43.00
Purchase #2	$42.70	8.765%	$46.4427	$46.44	$46.45	$46.40
Purchase #3	$118.79	7.652%	$127.8798	$127.88	$127.90	$127.90
Purchase #4	$51.39	13.741%	$58.4515	$58.45	$58.45	$58.50
Purchase #5	$150.34	12.773%	$169.5429	$169.54	$169.55	$169.50
Purchase #6	$133.74	12.749%	$150.7905	$150.79	$150.80	$150.80
Purchase #7	$37.25	10.126%	$41.0219	$41.02	$41.00	$41.00
7 purchase totals =	$572.95		$637.1733	$637.16	$637.20	$637.10