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	$71.53	9.239%	$78.1387	$78.14	$78.15	$78.10
Purchase #2	$66.62	10.269%	$73.4612	$73.46	$73.45	$73.50
Purchase #3	$203.43	5.161%	$213.929	$213.93	$213.95	$213.90
Purchase #4	$88.97	3.222%	$91.8366	$91.84	$91.85	$91.80
Purchase #5	$239.55	12.745%	$270.0806	$270.08	$270.10	$270.10
Purchase #6	$145.79	3.650%	$151.1113	$151.11	$151.10	$151.10
Purchase #7	$169.72	5.443%	$178.9579	$178.96	$178.95	$179.00
7 purchase totals =	$985.61		$1,057.5153	$1,057.52	$1,057.55	$1,057.50