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	$35.52	7.234%	$38.0895	$38.09	$38.10	$38.10
Purchase #2	$50.41	10.732%	$55.82	$55.82	$55.80	$55.80
Purchase #3	$41.42	4.264%	$43.1861	$43.19	$43.20	$43.20
Purchase #4	$55.50	11.552%	$61.9114	$61.91	$61.90	$61.90
Purchase #5	$102.54	6.323%	$109.0236	$109.02	$109.00	$109.00
Purchase #6	$148.68	4.286%	$155.0524	$155.05	$155.05	$155.10
Purchase #7	$161.88	4.661%	$169.4252	$169.43	$169.45	$169.40
7 purchase totals =	$595.95		$632.5082	$632.51	$632.50	$632.50