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	$171.84	9.368%	$187.938	$187.94	$187.95	$187.90
Purchase #2	$196.55	4.588%	$205.5677	$205.57	$205.55	$205.60
Purchase #3	$82.60	7.631%	$88.9032	$88.90	$88.90	$88.90
Purchase #4	$182.63	4.686%	$191.188	$191.19	$191.20	$191.20
Purchase #5	$53.79	10.775%	$59.5859	$59.59	$59.60	$59.60
Purchase #6	$144.38	6.835%	$154.2484	$154.25	$154.25	$154.20
Purchase #7	$223.46	10.644%	$247.2451	$247.25	$247.25	$247.20
7 purchase totals =	$1,055.25		$1,134.6763	$1,134.69	$1,134.70	$1,134.60