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	$61.40	13.175%	$69.4895	$69.49	$69.50	$69.50
Purchase #2	$76.56	13.430%	$86.842	$86.84	$86.85	$86.80
Purchase #3	$132.55	7.334%	$142.2712	$142.27	$142.25	$142.30
Purchase #4	$95.55	4.681%	$100.0227	$100.02	$100.00	$100.00
Purchase #5	$210.76	8.493%	$228.6598	$228.66	$228.65	$228.70
Purchase #6	$220.29	3.489%	$227.9759	$227.98	$228.00	$228.00
Purchase #7	$150.61	6.793%	$160.8409	$160.84	$160.85	$160.80
7 purchase totals =	$947.72		$1,016.1020	$1,016.10	$1,016.10	$1,016.10