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	$86.76	3.618%	$89.899	$89.90	$89.90	$89.90
Purchase #2	$136.90	4.174%	$142.6142	$142.61	$142.60	$142.60
Purchase #3	$203.42	5.841%	$215.3018	$215.30	$215.30	$215.30
Purchase #4	$69.99	4.164%	$72.9044	$72.90	$72.90	$72.90
Purchase #5	$13.57	3.371%	$14.0274	$14.03	$14.05	$14.00
Purchase #6	$115.46	7.504%	$124.1241	$124.12	$124.10	$124.10
Purchase #7	$7.48	9.498%	$8.1905	$8.19	$8.20	$8.20
7 purchase totals =	$633.58		$667.0614	$667.05	$667.05	$667.00