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	$67.80	5.150%	$71.2917	$71.29	$71.30	$71.30
Purchase #2	$187.31	6.147%	$198.8239	$198.82	$198.80	$198.80
Purchase #3	$172.66	4.169%	$179.8582	$179.86	$179.85	$179.90
Purchase #4	$173.71	3.377%	$179.5762	$179.58	$179.60	$179.60
Purchase #5	$137.60	10.182%	$151.6104	$151.61	$151.60	$151.60
Purchase #6	$100.97	10.427%	$111.4981	$111.50	$111.50	$111.50
Purchase #7	$55.58	3.262%	$57.393	$57.39	$57.40	$57.40
7 purchase totals =	$895.63		$950.0515	$950.05	$950.05	$950.10