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	$174.90	9.161%	$190.9226	$190.92	$190.90	$190.90
Purchase #2	$85.75	4.326%	$89.4595	$89.46	$89.45	$89.50
Purchase #3	$67.89	6.760%	$72.4794	$72.48	$72.50	$72.50
Purchase #4	$203.59	13.467%	$231.0075	$231.01	$231.00	$231.00
Purchase #5	$93.82	10.652%	$103.8137	$103.81	$103.80	$103.80
Purchase #6	$187.32	3.637%	$194.1328	$194.13	$194.15	$194.10
Purchase #7	$119.97	9.494%	$131.36	$131.36	$131.35	$131.40
7 purchase totals =	$933.24		$1,013.1755	$1,013.17	$1,013.15	$1,013.20