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	$196.59	8.490%	$213.2805	$213.28	$213.30	$213.30
Purchase #2	$27.50	3.526%	$28.4697	$28.47	$28.45	$28.50
Purchase #3	$46.75	9.822%	$51.3418	$51.34	$51.35	$51.30
Purchase #4	$81.98	4.804%	$85.9183	$85.92	$85.90	$85.90
Purchase #5	$115.63	8.408%	$125.3522	$125.35	$125.35	$125.40
Purchase #6	$115.79	10.398%	$127.8298	$127.83	$127.85	$127.80
Purchase #7	$47.90	11.832%	$53.5675	$53.57	$53.55	$53.60
7 purchase totals =	$632.14		$685.7598	$685.76	$685.75	$685.80