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	$78.43	11.870%	$87.7396	$87.74	$87.75	$87.70
Purchase #2	$163.29	10.660%	$180.6967	$180.70	$180.70	$180.70
Purchase #3	$229.40	6.332%	$243.9256	$243.93	$243.95	$243.90
Purchase #4	$135.88	11.517%	$151.5293	$151.53	$151.55	$151.50
Purchase #5	$121.65	4.775%	$127.4588	$127.46	$127.45	$127.50
Purchase #6	$138.35	9.593%	$151.6219	$151.62	$151.60	$151.60
Purchase #7	$109.86	5.485%	$115.8858	$115.89	$115.90	$115.90
7 purchase totals =	$976.86		$1,058.8577	$1,058.87	$1,058.90	$1,058.80