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	$187.57	4.870%	$196.7047	$196.70	$196.70	$196.70
Purchase #2	$186.63	7.164%	$200.0002	$200.00	$200.00	$200.00
Purchase #3	$86.43	13.469%	$98.0713	$98.07	$98.05	$98.10
Purchase #4	$21.79	12.838%	$24.5874	$24.59	$24.60	$24.60
Purchase #5	$166.93	11.414%	$185.9834	$185.98	$186.00	$186.00
Purchase #6	$224.28	10.221%	$247.2037	$247.20	$247.20	$247.20
Purchase #7	$132.57	6.469%	$141.146	$141.15	$141.15	$141.10
7 purchase totals =	$1,006.20		$1,093.6967	$1,093.69	$1,093.70	$1,093.70