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	$27.47	10.334%	$30.3087	$30.31	$30.30	$30.30
Purchase #2	$55.50	10.707%	$61.4424	$61.44	$61.45	$61.40
Purchase #3	$38.74	12.723%	$43.6689	$43.67	$43.65	$43.70
Purchase #4	$55.66	11.404%	$62.0075	$62.01	$62.00	$62.00
Purchase #5	$36.93	4.345%	$38.5346	$38.53	$38.55	$38.50
Purchase #6	$123.61	3.246%	$127.6224	$127.62	$127.60	$127.60
Purchase #7	$39.53	9.203%	$43.1679	$43.17	$43.15	$43.20
7 purchase totals =	$377.44		$406.7524	$406.75	$406.70	$406.70