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	$145.30	4.502%	$151.8414	$151.84	$151.85	$151.80
Purchase #2	$239.53	11.195%	$266.3454	$266.35	$266.35	$266.30
Purchase #3	$45.90	9.793%	$50.395	$50.40	$50.40	$50.40
Purchase #4	$28.79	9.597%	$31.553	$31.55	$31.55	$31.60
Purchase #5	$97.98	10.838%	$108.5991	$108.60	$108.60	$108.60
Purchase #6	$229.97	4.195%	$239.6172	$239.62	$239.60	$239.60
Purchase #7	$231.60	13.803%	$263.5677	$263.57	$263.55	$263.60
7 purchase totals =	$1,019.07		$1,111.9188	$1,111.93	$1,111.90	$1,111.90