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	$163.68	3.437%	$169.3057	$169.31	$169.30	$169.30
Purchase #2	$156.70	7.436%	$168.3522	$168.35	$168.35	$168.40
Purchase #3	$162.39	8.651%	$176.4384	$176.44	$176.45	$176.40
Purchase #4	$85.43	4.551%	$89.3179	$89.32	$89.30	$89.30
Purchase #5	$77.44	11.778%	$86.5609	$86.56	$86.55	$86.60
Purchase #6	$233.53	5.386%	$246.1079	$246.11	$246.10	$246.10
Purchase #7	$207.72	7.238%	$222.7548	$222.75	$222.75	$222.80
7 purchase totals =	$1,086.89		$1,158.8378	$1,158.84	$1,158.80	$1,158.90