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	$154.73	12.849%	$174.6113	$174.61	$174.60	$174.60
Purchase #2	$235.37	11.870%	$263.3084	$263.31	$263.30	$263.30
Purchase #3	$97.53	8.265%	$105.5909	$105.59	$105.60	$105.60
Purchase #4	$242.43	11.243%	$269.6864	$269.69	$269.70	$269.70
Purchase #5	$145.46	8.792%	$158.2488	$158.25	$158.25	$158.20
Purchase #6	$27.50	3.562%	$28.4796	$28.48	$28.50	$28.50
Purchase #7	$27.93	12.833%	$31.5143	$31.51	$31.50	$31.50
7 purchase totals =	$930.95		$1,031.4397	$1,031.44	$1,031.45	$1,031.40