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	$188.61	10.173%	$207.7973	$207.80	$207.80	$207.80
Purchase #2	$177.99	11.571%	$198.5852	$198.59	$198.60	$198.60
Purchase #3	$11.75	3.583%	$12.171	$12.17	$12.15	$12.20
Purchase #4	$120.86	9.171%	$131.9441	$131.94	$131.95	$131.90
Purchase #5	$172.40	5.242%	$181.4372	$181.44	$181.45	$181.40
Purchase #6	$131.50	6.404%	$139.9213	$139.92	$139.90	$139.90
Purchase #7	$131.85	12.142%	$147.8592	$147.86	$147.85	$147.90
7 purchase totals =	$934.96		$1,019.7153	$1,019.72	$1,019.70	$1,019.70