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	$137.62	9.694%	$150.9609	$150.96	$150.95	$151.00
Purchase #2	$38.33	7.813%	$41.3247	$41.32	$41.30	$41.30
Purchase #3	$9.28	9.389%	$10.1513	$10.15	$10.15	$10.20
Purchase #4	$164.48	6.419%	$175.038	$175.04	$175.05	$175.00
Purchase #5	$239.81	10.726%	$265.532	$265.53	$265.55	$265.50
Purchase #6	$180.79	3.759%	$187.5859	$187.59	$187.60	$187.60
Purchase #7	$206.83	8.102%	$223.5874	$223.59	$223.60	$223.60
7 purchase totals =	$977.14		$1,054.1802	$1,054.18	$1,054.20	$1,054.20