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	$87.66	5.437%	$92.4261	$92.43	$92.45	$92.40
Purchase #2	$142.88	6.417%	$152.0486	$152.05	$152.05	$152.00
Purchase #3	$146.69	13.813%	$166.9523	$166.95	$166.95	$167.00
Purchase #4	$76.88	12.836%	$86.7483	$86.75	$86.75	$86.70
Purchase #5	$116.62	12.664%	$131.3888	$131.39	$131.40	$131.40
Purchase #6	$101.68	7.620%	$109.428	$109.43	$109.45	$109.40
Purchase #7	$182.86	7.325%	$196.2545	$196.25	$196.25	$196.30
7 purchase totals =	$855.27		$935.2466	$935.25	$935.30	$935.20