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	$123.99	8.357%	$134.3518	$134.35	$134.35	$134.40
Purchase #2	$13.72	6.623%	$14.6287	$14.63	$14.65	$14.60
Purchase #3	$129.41	10.154%	$142.5503	$142.55	$142.55	$142.60
Purchase #4	$191.57	4.871%	$200.9014	$200.90	$200.90	$200.90
Purchase #5	$213.25	9.290%	$233.0609	$233.06	$233.05	$233.10
Purchase #6	$128.80	9.701%	$141.2949	$141.29	$141.30	$141.30
Purchase #7	$228.32	7.329%	$245.0536	$245.05	$245.05	$245.10
7 purchase totals =	$1,029.06		$1,111.8416	$1,111.83	$1,111.85	$1,112.00