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	$53.50	7.348%	$57.4312	$57.43	$57.45	$57.40
Purchase #2	$59.77	12.861%	$67.457	$67.46	$67.45	$67.50
Purchase #3	$85.88	5.639%	$90.7228	$90.72	$90.70	$90.70
Purchase #4	$171.45	6.260%	$182.1828	$182.18	$182.20	$182.20
Purchase #5	$148.90	3.541%	$154.1725	$154.17	$154.15	$154.20
Purchase #6	$160.32	10.270%	$176.7849	$176.78	$176.80	$176.80
Purchase #7	$213.99	13.746%	$243.4051	$243.41	$243.40	$243.40
7 purchase totals =	$893.81		$972.1563	$972.15	$972.15	$972.20