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	$64.26	4.506%	$67.1556	$67.16	$67.15	$67.20
Purchase #2	$111.30	7.381%	$119.5151	$119.52	$119.50	$119.50
Purchase #3	$158.53	6.873%	$169.4258	$169.43	$169.45	$169.40
Purchase #4	$116.92	9.207%	$127.6848	$127.68	$127.70	$127.70
Purchase #5	$221.85	10.746%	$245.69	$245.69	$245.70	$245.70
Purchase #6	$215.45	10.575%	$238.2338	$238.23	$238.25	$238.20
Purchase #7	$165.46	10.502%	$182.8366	$182.84	$182.85	$182.80
7 purchase totals =	$1,053.77		$1,150.5417	$1,150.55	$1,150.60	$1,150.50